Patent Application: US-201414206065-A

Abstract:
a polymer of formula : where : n is an integer from 10 to 5 , 000 ; m is an integer from 10 to 5 , 000 ; ar1 and ar3 are the same or different and are residues derived from a tetra - hydroxy aromatic monomer , the tetra - hydroxy aromatic monomer being wherein r is the same or different and is h or a c 1 - c 8 alkyl , c 2 - c 8 alkenyl or c 3 - c 8 cycloalkyl group ; and , ar2 and ar4 are the same or different and are residues derived from a tetra - halogenated aromatic monomer , the tetra - halogenated aromatic monomer being wherein x is f , cl or br , and r1 and r2 are the same or different and are wherein y is an integer from 1 to 8 ; with the proviso that when ar1 is the same as ar3 and ar2 is the same as ar4 , r1 and r2 are not both — cn is useful as a material for gas separation , vapor separation , adsorbents or catalysis .

Description:
hexafluorobenzene ( apollo scientific ltd . ), 4 - methoxylbenzenethiol ( matrix scientific ), 4 - bromo - 2 , 3 , 5 , 6 - tetrafluorobenzotrifluoride ( matrix scientific ), ethanethiol ( sigma - aldrich ), thiophenol ( sigma - aldrich ), 2 , 3 - naphthalenediol ( sigma - aldrich ), dimethylacetamide ( dmac , sigma - aldrich ), ferric chloride hexahydrate ( fecl 3 . 6h 2 o , anachemia ), sodium hydride ( 60 % nah dispersion in mineral oil , sigma - aldrich ), formic acid ( sigma - aldrich ), hydrogen peroxide solution 30 % ( w / w ) in h 2 o ( h 2 o 2 , aldrich ), anhydrous potassium carbonate ( k 2 co 3 , sigma - aldrich ), tetrahydrofuran ( thf , aldrich ) and toluene ( sigma - aldrich ) were reagent grade and used as received . 5 , 5 ′, 6 , 6 ′- tetrahydroxy - 3 , 3 , 3 ′, 3 ′- tetramethylspirobisindane ( ttsbi , sigma - aldrich ) was purified by re - crystallization from methanol . tetrafluoroterephthalonitrile ( tftpn , matrix scientific ) was purified by vacuum sublimation at 150 ° c . under inert atmosphere . pyridine ( sigma - aldrich ) was distilled from cah 2 . the structures of the polymeric materials were fully characterized using nuclear magnetic resonance ( nmr ) spectroscopy . nmr analyses were recorded on a varian unity inova spectrometer at a resonance frequency of 399 . 961 mhz for 1 h , 376 . 276 mhz for 19 f and 100 . 579 mhz for 13 c . 1 h and 19 f nmr spectra were obtained from samples dissolved in cdcl 3 or dmso - d 6 using a 5 mm pulsed field gradient indirect detection probe . 1 h - 13 c heteronuclear 2d experiments ( hsqc , hmbc ) were also obtained from the same indirect detection probe . 13 c nmr spectra were collected using a 5 mm broadband probe . the solvent signals ( cdcl 3 1 h 7 . 25 ppm , 13 c 77 . 00 ppm ; dmso - d 6 1 h 2 . 50 ppm , 13 c 39 . 43 ppm ) were used as the internal references . an external reference was used for 19 f nmr : cfcl 3 0 ppm . molecular weight and molecular weight distributions were measured by gpc using ultrastyragel ™ columns and thf as the eluent at a flow rate of 1 ml / min . the values obtained were determined by comparison with a series of polystyrene standards . elemental analysis was carried out with a thermoquest ™ chns — o elemental analyzer . polymer thermal degradation curves were obtained from thermogravimetric analysis ( tga ) ( ta instruments model 2950 ). polymer samples for tga were initially heated to 120 ° c . under nitrogen gas and maintained at that temperature for 1 h for moisture removal and then heated to 600 ° c . at 10 ° c ./ min for degradation temperature measurement . glass transition temperatures ( t g ) were observed from differential scanning calorimetry ( dsc ) ( ta instruments model 2920 ), and samples for dsc were heated at 10 ° c ./ min under a nitrogen flow of 50 ml / min , then quenched with liquid nitrogen and reheated at 10 ° c ./ min for the t g measurement . wide - angle x - ray diffraction ( waxd ) was used to investigate d - spacing . a bruker axs gadds instrument was utilized with co radiation of wavelength ( λ ) 1 . 789 å or cu kr radiation of wavelength ( λ ) 1 . 54 å . the value of the d - spacing was calculated by means of bragg &# 39 ; s law ( d = λ / 2 sin θ ), using θ of the broad peak maximum . dense polymer films for gas permeability measurements were prepared from 1 - 2 wt % polymer solutions in chloroform . polymer solutions were filtered through 0 . 45 μm polypropylene or poly ( tetrafluoroethylene ) ( ptfe ) filters and then cast into either glass or teflon ™ petri dishes in a glove box and allowed to evaporate slowly for 1 day . the films were soaked in methanol and dried in a vacuum oven at 100 ° c . for 24 h . the resulting membranes with thickness in the range of 60 - 80 μm were bright yellow and flexible . the absence of residual solvent in the films was confirmed by weight loss tests using tga . permeability coefficients ( p ) of n 2 , o 2 and co 2 were determined at 25 ° c . with a feed pressure of 50 psig and atmospheric permeate pressure using the constant - pressure / variable - volume method . the permeation flow was measured by a mass flow meter ( agilent adm 2000 ) or a bubble meter . permeability ( p ) was calculated by using a following equation : p = ( 273 t ) · ( ⅆ v ⅆ t ) · ( l δ ⁢ ⁢ p · a ) where dv / dt is the permeate - side flow rate ( cm 3 / s ), t is the operation temperature ( k ) and δp is the gas pressure differential between the upstream and downstream sides of the membrane . the membrane effective area ( a ) was 9 . 6 cm 2 . into a 50 ml three - necked flask equipped with a magnetic stirrer , an argon inlet and a condenser , thiophenol ( 2 . 42 g , 0 . 022 mol ), nah ( 0 . 88 g , 0 . 022 mol ), dmac ( 5 ml ) were added . the mixture was cooled to − 20 ° c . using an ice salt bath ( nacl / ice = 3 : 1 , w : w ) and stirred for 1 h . 4 - bromo - 2 , 3 , 5 , 6 - tetrafluorobenzotrifluoride ( 5 . 94 g , 0 . 02 mol ) in 5 ml dmac was added dropwise , then the temperature was gradually increased to room temperature . after stirring at room temperature for 6 h , the reaction mixture was poured into water and the crude product was washed 3 times . the orange color oil was extracted with chloromethane and dried over mgso 4 . after removal of chloromethane , the resulting crude heptafluoro - p - tolylphenylsulfide was oxidized with formic acid ( 5 ml ) and h 2 o 2 ( 30 %) ( 6 g ) at 50 ° c . for 2 h , resulting in a white - yellow solid sulfone product that was initially purified by chromatography ( using 1 / 1 v / v dichloromethane / hexane ). pure product in the form of white needle crystals was obtained by recrystallization from hexane . yield : 65 %. mp : 134 ° c . elem . anal . calcd for c 13 h 5 f 7 o 2 s ( 358 . 23 g / mol ): c , 43 . 95 %; h , 1 . 41 %; s , 8 . 95 %. found : c , 43 . 24 %; h , 1 . 39 %; s , 8 . 95 %. 1 h nmr ( chloroform - d ) δ 8 . 09 ( d , j = 8 . 0 hz , 2h ), 7 . 73 ( t , j = 8 . 0 hz , 1h ), 7 . 62 ( t , j = 8 . 0 hz , 2h ); 19f nmr ( chloroform - d ) δ − 57 . 6 ( t , j = 22 . 5 hz , 3f ), − 134 . 3 ( m , 2f ), − 136 . 9 ( m , 2f ). 13c nmr ( chloroform - d ) δ 145 . 8 - 143 . 0 ( d , j = 264 hz , 2h ), 145 . 5 - 142 . 7 ( d , j = 264 hz , 2h ), 139 . 9 ( s , 1h ), 135 . 3 ( s , 1h ), 129 . 8 ( s , 2h ), 128 . 2 ( s , 2h ), 125 . 3 - 125 . 0 ( t , j = 14 hz , 1h ), 124 . 1 - 115 . 9 ( q , j = 275 hz , 1h ), 114 . 2 - 113 . 9 ( m , 1h ). a literature procedure was employed [ toda 1989 ]. a mixture of 2 , 3 - naphthalenediol ( 16 g , 0 . 1 mol ) and fecl 3 . 6h 2 o ( 27 g , 0 . 2 mol ) was finely powdered by agate mortar and pestle . the mixture was then put in a test tube and irradiated with ultrasound at 50 ° c . for 1 h . decomposition of the reaction mixture with dilute hcl gave crude 2 , 2 ′ 3 , 3 ′- tetrahydroxy - 1 , 1 ′- dinaphthyl in 85 % yield . the tetrol was recrystallized from thf three times to give white needle powder at 53 % yield . mp & gt ; 300 ° c . 1 h nmr ( dmso - d 6 ) δ 6 . 80 - 6 . 82 ( d , j = 8 . 0 hz , 2h ), 6 . 94 - 6 . 98 ( t , j = 8 . 0 hz , 2h ), 7 . 14 - 7 . 18 ( t j = 8 . 0 hz , 2h ), 7 . 24 ( s , 2h ), 7 . 64 - 7 . 62 ( d , j = 8 . 0 hz , 2h ), 8 . 41 ( s , oh ), 10 . 07 ( s , oh ) elem . anal . calcd for c 20 h 14 o 4 ( 318 . 32 g / mol ): c , 75 . 46 %; h , 4 . 43 % found : c , 75 . 41 %; h , 4 . 56 %. three dithioethers were synthesized by modifying known procedures [ kulka 1959 ; robson 1963 ; langille 1972 ]. generally , into a 250 ml three - neck flask equipped with a magnetic stirrer , an argon inlet and a condenser , a thiol ( 54 mmol ), nah ( 54 mmol ), and dry pyridine ( 15 ml ) were added . the reaction mixture was cooled to − 20 ° c . using an ice salt bath ( nacl : ice = 3 : 1 , w / w ), and stirred for 1 h . thereafter , the reaction mixture was added dropwise into hexafluorobenzene ( 27 mmol ) and the temperature was gradually increased to room temperature . after stirring at room temperature for 30 min , the reaction mixture was refluxed for another 20 min and then poured into water . the crude product was washed with 8 n hydrochloric acid and extracted with dichloromethane and dried over mgso 4 . after purifying , the dithioethers ( 5 g ) were oxidized with formic acid ( 15 ml ) and h 2 o 2 ( 30 %, 20 g ) and maintained at 100 ° c . for 24 h , resulting in white disulfone products , which were collected and purified . the dithioether was purified by chromatography ( using 1 / 4 , v / v chloromethane / hexane ). pure product in the form of white needle crystals was obtained by recrystallization from hexane . yield : 48 %. mp : 109 - 110 ° c . elem . anal . calcd for c 18 h 10 f 4 s 2 ( 366 . 4 g / mol ): c , 59 . 01 %; h , 2 . 75 %; s , 17 . 5 %. found : c , 58 . 51 %; h , 2 . 69 %; s , 17 . 62 %. 1 h nmr ( chloroform - d ) δ 7 . 43 - 7 . 39 ( m , 4h ), 7 . 35 - 7 . 29 ( m , 6h ). 19 f nmr ( chloroform - d ) δ − 132 . 4 ( s , 4f ). 13 c nmr ( chloroform - d ) δ 146 . 9 ( d , j = 251 hz ), 132 . 5 ( s ), 131 . 0 ( s ), 129 . 4 ( s ), 128 . 1 ( s ), 115 . 3 ( m ). after oxidation , the raw tfbpsb disulfone monomer was recrystallized from dimethylformamide ( dmf ), to give white needle crystals in a yield of 81 %. mp & gt ; 300 ° c . elem . anal . calcd for c 18 h 10 f 4 o 4 s 2 ( 430 . 39 g / mol ): c , 50 . 23 %; h , 2 . 34 %; s , 14 . 9 %. found : c , 49 . 57 %; h , 2 . 042 %; s , 14 . 89 %. 1 h nmr ( dmso - d 6 ) δ 8 . 03 ( d , j = 8 . 0 hz , 4h ), 7 . 85 ( t , j = 8 . 0 hz , 2h ), 7 . 71 ( t , j = 8 . 0 hz , 4h ). 19 f nmr ( dmso - d 6 ) δ − 135 . 6 ( s , 4f ). 13 c nmr ( dmso - d 6 ) δ 145 ( dm , j = 256 hz ), 139 . 2 ( s ), 135 . 6 ( s ), 129 . 9 ( s ), 127 . 7 ( s ), 124 . 2 ( m ). the dithioether was purified by chromatography ( using 1 / 2 , v / v chloromethane / hexane ). pure product in the form of white flake crystals was obtained by recrystallization from hexane . yield : 51 %. mp : 104 ° c . elem . anal . calcd . for c 20 h 14 f 4 o 2 s 2 ( 426 . 45 g / mol ): c , 56 . 33 %; h , 3 . 31 %; s , 15 . 04 %. found : c , 55 . 30 %; h , 3 . 04 %; s , 15 . 01 %. 1 h nmr ( chloroform - d ) δ 7 . 46 ( d , j = 8 hz , 4h ), 6 . 84 ( d , j = 8 hz , 4h ), 3 . 80 ( s , 6h ). 19 f nmr ( chloroform - d ) δ − 133 . 7 ( s , 4f ). 13 c nmr ( chloroform - d ) δ 160 . 2 ( s ), 146 . 7 ( dm , j = 251 hz ), 134 . 8 ( s ), 122 . 4 ( s ), 114 . 8 ( s ), 109 . 8 ( m ), 55 . 3 ( s ). after oxidation , the crude tfbmpsb disulfone monomer was recrystallized from dmf , to give white needle crystals in 78 % yield . mp & gt ; 300 ° c . elem . anal . calcd . for c 20 h 14 f 4 o 6 s 2 ( 490 . 45 g / mol ): c , 48 . 98 %; h , 2 . 88 %; s , 13 . 08 %. found : c , 48 . 38 %; h , 3 . 047 %; s , 13 . 01 %. 1 h nmr ( dmso - d 6 ) δ 7 . 95 ( dd , j = 8 hz , 4h ), 7 . 20 ( dd , j = 8 hz , 4h ), 3 . 86 ( s , 6h ). 19 f nmr ( dmso - d 6 ) δ − 136 . 2 ( s , 4f ). 13 c nmr ( dmso - d 6 ) δ 161 . 3 ( s ), 144 . 5 ( dm , j = 251 hz ), 133 . 3 ( s ), 130 . 3 ( s ), 123 . 1 ( m ), 115 . 2 ( s ), 54 . 91 ( s ). the 1 , 4 - bis ( ethylthio )- 2 , 3 , 5 , 6 - tetrafluorobenzene was oxidized without purification . the crude disulfone was recrystallized in dmf and toluene to give white needles of tfbesb disulfone monomer in 72 % yield . mp : 239 ° c . elem . anal . calcd . for c 10 h 10 f 4 o 4 s 2 ( 334 g / mol ): c , 35 . 93 %; h , 3 . 02 %; s , 19 . 18 %. found : c , 35 . 65 %; h , 2 . 91 %; s , 18 . 65 %. 1 h nmr ( dmso - d 6 ) δ 3 . 61 ( q , j = 8 hz , 4h ), 1 . 27 ( t , j = 8 hz , 6h ). 19 f nmr ( dmso - d 6 ) δ − 135 ( s , 4f ). 13 c nmr ( dmso - d 6 ) δ 142 . 4 ( dm , j = 251 hz ), 129 . 94 ( m ), 51 . 2 ( s ), 6 . 4 ( s ). 2 , 3 , 7 , 8 - tetrafluorothianthrene was synthesized by modifying a known procedure [ bock 1982 ]. thus , into a 250 ml three - neck flask equipped with a magnetic stirrer , an argon inlet and a condenser , difluorobenzene ( 20 mmol ), alcl 3 ( 60 mmol ), and dry dichloromethane ( 50 ml ) were added . the reaction mixture was cooled to 0 - 20 ° c . using an ice salt bath ( nacl : ice = 3 : 1 , w / w ), and stirred for 1 h . thereafter , the reaction mixture was added dropwise into s 2 cl 2 ( 20 mmol ) and the temperature was gradually increased to room temperature . after stirring at room temperature for 2 hour , the reaction mixture was refluxed for another 20 min and then poured into water . the crude product was washed with 8 n hydrochloric acid and extracted with dichloromethane and dried over mgso 4 . after removed the dichloromethane , the 2 , 3 , 7 , 8 - tetrafluorothianthrene ( 5 g ) was recrystallized from hexane to give white needle crystals in a yield of 49 %. mp = 108 ° c . 1 h nmr ( chloroform - d ) δ 7 . 309 ( t , j = 8 . 0 hz , 4h ). 19 f nmr ( chloroform - d ) δ − 136 . 4 ( s , 4f ). 13 c nmr ( chloroform - d ) δ 150 . 07 ( dd , j = 252 hz ), 131 . 34 ( t , j = 5 . 3 hz ), 117 . 64 ( m ). to synthesize the tftot monomer , 20 g of 2 , 3 , 7 , 8 - tetrafluorothianthrene was oxidized with formic acid ( 100 ml ) and cro 3 ( excess ) and maintained at 100 ° c . for 24 h , resulting in white 2 , 3 , 7 , 8 - tetrafluoro - 5 , 5 ′, 10 , 10 ′- tetraoxidethianthrene ( tftot ), which were collected and recrystallized from dmf to give white flake crystals in a yield of 92 %. mp & gt ; 300 ° c . elem . anal . calcd for c 12 h 4 f 4 o 4 s 2 ( 352 . 28 g / mol ): c , 40 . 91 %; h , 1 . 14 %; s , 18 . 20 %. found : c , 41 . 13 %; h , 1 . 09 %; s , 18 . 26 %. 1 h nmr ( dmso - d 6 ) δ 8 . 087 ( t , j = 8 . 0 hz , 4h ). 19 f nmr ( dmso - d 6 ) δ − 123 . 185 ( t , j = 8 . 0 hz , 4f ). into a 100 ml three - necked flask equipped with a magnetic stirrer , an argon inlet , and a dean - stark trap , tftpn ( 2 . 001 g , 0 . 01 mol ) and ttsbi ( 3 . 404 g , 0 . 01 mol ), anhydrous k 2 co 3 ( 4 . 14 g , 0 . 03 mol ), dmac ( 20 ml ), and toluene ( 10 ml ) were added . during the initial 20 - 30 minutes , a small amount of water was observed in the dean - stark trap . the mixture was refluxed at 160 ° c . for 40 min , and then the viscous solution was poured into methanol . a yellow flexible threadlike polymer was obtained . the polymer product was dissolved into chloroform and re - precipitated from methanol . the resulting polymer was refluxed for several hours with deionized water , and dried at 100 ° c . for 48 h . comparison of pim - 1 properties for pim - 1 polymers produced by a process of the present invention and by a prior art process pim - 1 polymers were produced using a standard prior art procedure ( budd 2004a ] and a procedure in accordance with the present invention . reaction conditions are shown in table 1 . various physical properties of the pim - 1 polymers produced were determined and are shown in table 2 . it is evident from table 2 that the process of the present invention results in polymers having larger m n , which is advantageous for materials for gas separation membranes , further , as evidenced by the m w / m n ratio , pim - 1 polymers produced by the present invention have less cyclic and cross - linked fractions . furthermore , mechanical properties like tensile stress and strain are improved in pim - 1 polymers produced by the process of the present invention . finally , pim - 1 polymers produced by the present process have enhanced surface area ( s bet ). a series of tfmpspim ladder polymers 1 - 4 were synthesized by polycondensation of ttsbi , hftps and tftpn ( with the molar ratio 1 : 1 : 0 ; 3 : 2 : 1 ; 2 : 1 : 1 ; 3 : 1 : 2 ) using a procedure similar to that of example 5 , and illustrated in scheme 2 . alsop et al . previously reported the synthesis of hftps by oxidation of heptafluoro - p - tolylphenylsulfide , obtained from the reaction of thiophenol with octafluorotoluene [ alsop 1962 ]. as far as we are aware , hftps has not previously been utilized as a monomer in a polymerization reaction . the present synthetic method is different from the previous report and comprises two steps as shown in scheme 2 . in the first step , the bromine atom in 4 - bromo - 2 , 3 , 5 , 6 - tetrafluorobenzotrifluorde is displaced by thiophenol using nah at − 20 ° c . both f - ar and br - ar react with thiophenols under basic conditions by aromatic nucleophilic substitution reaction , but the reactivity is different . at higher temperatures , f - ar is more reactive , while at lower temperatures , br - ar is more easily displaced , since — br is an efficient leaving group specifically for reactions with thiophenolates . elevated temperatures ( above 60 ° c .) or longer reaction times would lead to more byproducts , indicating that the comparative selectivity of thiophenol group decreases . k 2 co 3 can be also used as a base for this reaction at these conditions . however , at lower temperatures , water cannot be removed and it continues to react with ar - f to form ar - oh , thereby reducing the yield . a small amount of cah 2 was added to the reaction at the beginning to eliminate the water efficiently . although the resulting ca ( oh ) 2 was basic , it does not react readily with f - ar at low temperature due to the poor solubility . the crude product was oxidized without purification . the thioether could be completely converted to sulfone using excess h 2 o 2 in a heterogeneous formic acid suspension at 50 ° c . within 2 hours . in terms of its use as a monomer for ladder polymers , the new monomer relies on the electron withdrawing power of sulfone , rather than nitrile used in the synthesis of pim - 1 . the ladder pims ( including tfmpspim and pim - 1 ) containing — cf 3 , — so 2 c 6 h 5 , and — cn groups , were synthesized by snar polycondensation using various feed ratios of ttsbi / hftps / tftpn , so that polymers with different molar percentages of — cn and — cf 3 /— so 2 c 6 h 5 ( scheme 2 ) were obtained . the ideal structures of the ladder polymers are linear chains without crosslinking . the characterization results are listed in table 3 . the polymers are named tfmpspim1 - 4 , where pim stands for polymer of intrinsic microporosity , tfm and ps refers to trifluoromethyl and phenylsulfonyl respectively . the synthesis of ladder polymers with substantially reduced amounts of cyclic species or crosslinking was accomplished using new polymerization conditions applied to pims . a higher polymerization temperature of 160 ° c . and higher monomer concentrations ( monomer : solvent = 1 mmol : 2 ml ) in dmac were used compared with the previously reported polymerization conditions conducted at lower temperatures . dmac is largely compatible with both the monomer salts and growing polymer chain at this temperature . in addition , excess toluene ( toluene : dmac = 4 : 1 v / v ) was introduced into the reaction not only to remove generated water , but to provide solubility enhancement of the polymer . in a similar reaction carried out in the absence of excess toluene , crosslinked polymer formed readily in the latter stages of polymerization ( approx . the last 10 min ). the new high - temperature polymerization procedure for pim - 1 reported here led to high molecular weight polymers within 40 min . compared with the originally reported pim synthesis [ budd 2004b ], the reaction conditions reported here require less time and the explosion - like polycondensation is relatively easy to control . in contrast , with typical nucleophilic aromatic substitution polycondensation reactions to produce poly ( aryl ether ) s , the formation of the ladder polymers is more complicated . as shown in scheme 1 and scheme 2 , each monomer has four reactive groups , greatly increasing the susceptibility for crosslinking to occur . however , using the present reaction conditions , gpc results ( table 3 ) show that high molecular weight polymers ( m n & gt ; 55 , 000 da ) were obtained and the polydispersity index is approximately 2 . 0 , which is consistent with the results of typical polycondensation reactions in which each monomer has two reactive sites . on gpc curves ( fig4 ), there is no shoulder peak in the low or high molecular weight region around the main peak , indicating that it is a clean reaction with few crosslinked or cyclic structures . gpc results also showed that tfmpspim1 - 4 polymers with higher molecular weight as compared to pim - 1 were obtained under the same reaction condition . the m n of the polymer decreased as the ratio of monomer hftps in the copolymer was reduced . the homopolymer prepared from hftps had the highest m n , while pim - 1 homopolymer had the lowest . a plausible explanation is that the — cf 3 group and — so 2 c 6 h 5 enhance the solubility of the polymer and growing chain , so that the polymer chains are unfolded , uncoiled and unpacked , and the chain - growth step reaction is facilitated . meanwhile , the — f and — oh on neighboring aromatic rings readily react with each other and form ladder structures with less propensity for crosslinking . the mechanical properties of the ladder polymer series are listed in table 3 . tensile stress at break and tensile strain at break decreased due to the introduction of increasing amounts of — cf 3 and — so 2 c 6 h 5 into the polymer chain . in the series from pim - 1 to tfmpspim4 , tensile strain at break drops off sharply from 11 . 2 % to 5 . 6 % while almost maintaining the same tensile stress at break ( from 47 . 1 to 46 . 2 mpa ), which implies that the polymer had additional rigidity due to the introduction of pendant — cf 3 and — so 2 c 6 h 5 groups . the tfmpspim1 and pim - 1 homopolymers and tfmpspim2 - 4 copolymers were fully characterized by 1 h , 13 c and 19 f nmr spectroscopy ( 19 f nmr ( chloroform - d ) − 56 . 2 ppm ( s , 3f )). carbon nmr was particularly useful as there are many quaternary carbon atoms on these polymers . stacked 1 h nmr spectra of tfmpspim1 , pim - 1 and tfmpspim3 are displayed in fig2 while 13 c spectra of the same polymer series are displayed in fig3 . the aliphatic and aromatic hydrogen signals of pim - 1 and tfmpspim1 were unambiguously assigned with the help of 2d hsqc and hmbc . long range c — h correlations involving c1 with ch 3 ( 2jc - c — h ) and h6 ( 3jc - c — c — h ) helped differentiate the h6 signal from h9 . most pim - 1 carbon signals were assigned using direct hsqc c — h couplings . all the quaternary carbon atom signals from the ttsbi monomer part were identified by multiple bonds c — h correlations ( hmbc ) with previously assigned proton frequencies . the absence of hydrogen atoms on the tftpn monomer results in no signals in 2d hsqc , hmbc nmr . therefore c10 ′, c11 ′ and — cn were assigned based on their chemical shifts . c10 ′ is strongly deshielded by the electronegative oxygen atom and was therefore easily assigned as the signal at the highest frequency ( 139 ppm ). on the other hand , c11 ′ is shielded by the electron donating effect through delocalization of the same oxygen atoms . c11 ′ is sandwiched between two c — o groups and will therefore be strongly shielded and shifted to very low frequencies hence the peak at 94 ppm . the last quaternary carbon , — cn , appears in the typical — cn range ( 109 ppm ). a 13 c nmr prediction spectrum was obtained ( acd labs prediction software , v . 10 . 04 , december 2006 ) in order to compare the actual and predicted chemical shifts for c10 ′, c11 ′ and cn . the predicted chemical shifts were within 2 ppm for c10 ′ and c11 ′ and within 7 ppm for cn , hence validating our peak assignments based on nmr knowledge . the 1 h and 13 c nmr spectra of tfmpspim1 homopolymer were obviously similar to those of pim - 1 homopolymer due to their identical ttsbi monomer residue within the backbone . the additional signals arising from the new monomer were readily assigned in both 1 h and 13 c nmr with the help of 2d hmbc and hsqc . as before , the c — o carbon atoms c10 ′ and c12 ′ were assigned to high frequencies ( 137 - 141 ppm ). the — cf 3 and c11 ′ were identified by their spin - couplings with the 19 f atoms ( 1jc - f = 277 hz , 2jc11 ′- f ≈ 30 hz ). the 1 h and 13 c nmr spectra of the copolymer tfmpspim3 prepared from the monomer ratio 2 ttsbi : 1 hftps : 1 tftpn are shown as the lower spectra in fig2 and 3 . as expected , these spectra display the same characteristics as the two fully characterized homopolymers pim - 1 and tfmpspim1 . the specific low frequency ( 94 ppm ) c11 ′ of pim - 1 and the specific quartet — cf 3 of tfmpspim1 are clearly visible in the 13 c nmr spectrum . furthermore , the experimental ratio of intensity values for proton h - 15 , 16 , 17 compared with h - 6 , 9 is exactly 5h : 8h , as expected for two repeat units of the tfmpspim3 copolymer . finally , the 19 f nmr spectra ( not shown ) were collected for all three polymers . only tfmpspim1 and tfmpspim3 showed a signal at ca . 56 ppm which is characteristic of a — cf 3 group . it is worthwhile mentioning that no aromatic f signal was observed . thermal analyses for tfmpspim and pim - 1 were carried out and the results are summarized in table 4 . all the polymers have no discernable t g in the measured range of 50 ° c . to 350 ° c . tga experiments showed that all the polymers have excellent thermal stabilities and the actual onset temperature of decomposition in nitrogen is above 350 ° c . there is also some trend between this temperature and monomer ratio . generally , nitrile - containing polymers have high thermal stability , likely due to strong dipolar interactions . table 4 shows that with increasing molar content of — cn in the polymers , the onset of thermal decomposition also increased . however , tfmpspim homopolymer and copolymers all showed very good thermal stability even after the replacement of nitrile with — cf 3 and pendant — so 2 c 6 h 5 groups . fractional free volume ( ffv ) increased with increasing nitrile content , suggesting that tfmpspims with increasing — cf 3 and — so 2 c 6 h 5 pendant groups pack interchain space more efficiently than pim - 1 , as shown in table 5 . where v f is the free volume , v sp is the specific volume . membrane samples had a density in the range 1 . 06 - 1 . 21 g cm 3 , as determined by measurements of their weight in air and in ethanol . v w is the specific van der waals volume calculated using the group contribution method of bondi [ bondi 1964 ; van krevelen 1990 ]. these assumptions are supported by the x - ray diffraction measurements shown in fig5 , which reveal that all the polymers were amorphous . three broad peaks were observed for all polymers . the peak at higher angles ( 4 . 9 å ) can be attributed to the chain - to - chain distance of space efficiently packed chains . the second peak , corresponding to more loosely packed polymer chains with a d - spacing of about 6 . 50 å , is attributed to polymers maintaining their conformation with micropores between the chains [ weber 2007 ]. the exact d - spacing values were calculated from waxd spectra by bragg &# 39 ; s law and are listed in table 5 . these values are consistent with the explanation of the free volume theory . the d - spacing of tfmpspim1 homopolymer is about 6 . 30 å and it becomes larger with decreasing molar amounts of — cf 3 and — so 2 c 6 h 5 groups in the main chain , suggesting that the — cf 3 and — so 2 c 6 h 5 pendant groups affect the polymer chain packing and decrease polymer d - spacing , possibly by inter - chain space - filling . the third peak at a d - spacing of about 10 å corresponds to the distance between the spiro - carbon atoms , which is about 10 - 15 å for pim - 1 and is very similar to the calculated distances for tfmpspim1 - 4 . the significance of the distance between the spiro - carbon centers is that the relatively planar rigid chain segments change direction and are skewed at these points , preventing efficient chain packing . a tradeoff relationship is usually observed between permeability ( p ) and ideal selectivity ( α ) for common gases in glassy or rubbery polymers , i . e ., higher permeability is gained at the cost of lower selectivity and vice versa . upper bound performance lines for the relationship between gas permeability and selectivity have been proposed by robeson [ robeson 1991 ]. pure - gas permeability coefficients ( p ) were measured on dense films ( pim - 1 , tfmpspim1 - 4 ) for o 2 , n 2 , and co 2 and a summary of these p values and ideal selectivities for various gas pairs are shown in table 6 . as can be seen in table 6 , tfmpspim1 - 4 were significantly more selective than pim - 1 for all gases . although the permeability of o 2 is reduced with increasing amounts of — cf 3 and — so 2 c 6 h 5 groups , tfmpspim1 - 4 permeability / selectivity data points are all above the upper bound line reported by robeson , as shown in fig6 . fig6 illustrates the trade - off between o 2 permeability and o 2 / n 2 selectivity of pim - 1 , tfmpspim1 - 4 membranes relative to the robeson upper bound line . ∇ is data from budd et al . which are for measurements reported at 200 mbar ( 2 . 9 psia ) feed pressure at 30 ° c . [ budd 2005b ]. δ is data from staiger et al . which are for measurements reported at 4 atm ( 58 . 8 psia ) feed pressure 35 ° c . [ staiger 2008 ]. in comparison with pim - 1 , which was tested under the same conditions , tfmpspim1 - 4 have significantly higher o 2 / n 2 and co 2 / n 2 selectivity . from a material and structural viewpoint , chain rigidity imparts increased selectivity but lower permeability , whereas greater interchain distance imparts higher permeability but lower selectivity . the — cf 3 and — so 2 c 6 h 5 groups in tfmpspim1 - 4 are hidden within the spirocyclic main chain structure , which maintains its zigzag conformation . while these pendant groups do not increase ffv , they increase chain stiffness and likely have an effect of inter - chain space filling . compared to data reported by budd et al . for films cast from tetrahydrofuran and measured at low gas feed pressure , the pure - gas oxygen permeability of pim - 1 reported for the present invention ( about 1 , 133 barrer ) is about 3 - times higher , but with a reduction in oxygen / nitrogen selectivity from 4 to 3 . 2 ( table 6 ). however , data for the present invention is more consistent with that of staiger et al ; the pure - gas permeabilities and selectivities of a pim - 1 film made from methylene chloride are similar to our data for a chloroform - solution - cast pim - 1 film . the gas permeation properties of highly rigid glassy polymers depend strongly on film formation protocols , such as casting solvent type and drying conditions [ moe 1988 ]. conformational analysis of tfmpspim1 and pim - 1 was modeled with three repeat unit lengths to study the effect and distribution of — cf 3 and — so 2 c 6 h 5 on chain geometry and steric interaction . the calculation results of geometry optimization with energy minimization using the amber method provides a visualization of major conformational changes occurring in the polymers , as shown in fig7 . the chains of pim - 1 homopolymer containing — cn side groups , shown for comparison , have a relatively spiro - zigzag linear and regular ladder structure , which would lead to less chain packing . compared with pim - 1 , tfmpspim1 homopolymer showed a similarly unperturbed coil conformation . although — cf 3 and — so 2 c 6 h 5 are more bulky than the — cn group , they do not change the spiro - zigzag ladder chain . in addition , the rigidity of the ladder polymer chain with — cf 3 and — so 2 c 6 h 5 groups can be enhanced by hindering bond distortion within the ladder chain ; hence selective diffusion ability can be improved . presumably , the pendant phenylsulfonyl group resides within the inter - chain free - volume and also acts to reduce permeability , while increasing selectivity . this is in good agreement with the gas permeation results . the molecular modeling result may help to explain why , as compared to pim - 1 , the co - effects of tfmpspim improve their gas selectivity without overall loss of performance relative to the upper bound line . preparation and characterization of pim ladder polymers containing tetrahydroxy dinaphthyl ( thdn ) monomer in order to investigate the effect of the spatially twisted structure in the polymer chain , this example focuses on the synthesis of copims derived from ttsbi , tftpn and thdn . the resulting copolymers were analyzed by gpc , tga , nitrogen sorption , and gas permeabilities were measured . scheme 3 gives an overview of the reaction scheme to prepare thdnpim copolymers . pim copolymers derived from various feed ratios of ttsbi / thdn / tftpn monomers were prepared by the aromatic nucleophilic polycondensation at 160 ° c . for 120 min in a manner similar to example 5 . thus , into a 100 ml three - necked flask equipped with a magnetic stirrer , an argon inlet , and a dean - stark trap , with different ratio of monomers ( thdn , ttsbi and tftpn ), anhydrous k 2 co 3 , dmac ( monomers : dmac = 1 : 3 . 5 w : w ) and toluene were added . the mixture was refluxed at 160 ° c . for 120 min , and then the viscous solution was poured into methanol . a yellow flexible threadlike polymer was obtained . the polymer product was dissolved in chloroform and reprecipitated from methanol . the resulting polymer was refluxed for several hours with deionized water , and dried at 100 ° c . for 48 h . the properties of the pims are summarized in table 7 . for comparison , pim - 1 was prepared under identical reaction conditions from ttsbi and tftpn . it should be noted that pim - 1 prepared at this temperature for shorter reaction time ( 40 minutes ) produced high molecular weight with narrow polydispersity . table 7 contains the approximate molecular weights and polydispersities of the copolymers , as determined by gpc against polystyrene standards . a thdnpim homopolymer is abbreviated as thdnpim - 100 and copolymers as thdnpim - 66 , thdnpim - 50 and thdnpim - 33 , where 66 , 50 and 33 refer to the percentage of thdn / tftpn ( molar ratio ) in the polymer chain . cyclic oligomers and cross - linking can be effectively reduced by using polycondensation reaction conditions of elevated temperature at 160 ° c . and high monomer concentrations . toluene was also added to increase of solubility of tetraphenol salts and growing polymer chain . within 40 min , the pim - 1 polymerization under optimum reaction conditions ( 160 ° c . and monomers : dmac = 1 mmol : 2 ml ) proceeded smoothly and no evidence of cross - linking was detected . it was observed that pim - 1 was prone to high molecular weight fractions and possible cross - linking when the reaction time exceeded 90 min under same conditions ( polydispersity values up to 15 ), which resulted in limited m n . in the absence of toluene in reaction system , crosslinking occurred rapidly , within 30 min . as shown in fig8 , there are several shoulder peaks in the high molecular weight region around the main peak of pim - 1 prepared at a reaction time of 120 min , indicating high molecular weight fractions and possible cross - linking . in this example , pim - 1 was prepared under the same conditions as thdnpim . table 7 shows that the polydispersities of thdnpim copolymers is in the range of 1 . 8 - 2 . 3 , compared to over 10 for pim - 1 prepared at the extended 120 min reaction time . it is interesting to note that as the molar ratio of ttsbi in thdnpim copolymers is increased up to thdnpim - 50 , a high m n can be obtained with a low polydispersity . at higher molar ratios beyond thdnpim - 50 , m n values above 10 , 000 could still be obtained under these conditions , with low polydispersities . in the case of thdnpim - 33 , a high molecular weight and low polydispersity was obtained , with no evidence of cross - linking . thus , under the same reaction conditions ( 160 ° c ., 120 min ), molecular weight broadening and cross - linking are efficiently reduced by introducing a certain ratio of thdn into the polymer chain , and high molecular weight copolymer can be obtained . a plausible explanation is that ttsbi has a higher reactivity than thdn , and its concentration was decreased by introducing thdn into the copolymerization system , resulting in less cross - linking . on another hand , although high temperature and high concentration polymerization conditions were applied in this reaction , a high molecular weight homopolymer from tftpn and thdn still could not be obtained , most likely due to steric hindrance induced by the spatially twisted dinaphthyl center . although the m n of thdnpims - 100 homopolymer is higher ( m n = 10 , 000 da ) than that previously reported [ mckeown 2006a ]( m n = 3 , 000 ), it is still insufficient to fabricate mechanically strong films for gas permeability measurements . fig8 shows that as the molar content of thdn monomer increases , the low molecular weight of the resulting thdnpim copolymers decrease . in addition , thdnpim - 100 and − 66 have a significant amount of low molecular weight fractions . fig9 shows that thdnpim - 100 ( the homopolymer ) consists mainly of cyclics and oligomers , which have two — f and two — oh groups at the polymer chain terminus . an insight as to why cyclization is favoured in chain step - growth of thdnpim - 100 was found by using the computer molecular modeling analysis . energy minimized structural analysis of thdnpim - 100 and pim - 1 of four repeat units was performed by using hyperchem ™ 7 . 0 software . in fig1 , a visual indication of major conformational changes in the polymer chain units was obtained by the calculated results of geometry optimization with minimum energy using the amber method . compared to the 90 ° zigzag chains observed for pim - 1 , the thdnpim - 100 chain has a twist angle of about 60 ° for each unit . the reactive end - groups are situated in a conformation conducive to form cyclic species , since the chain is more foldable and compact . with the incorporation of increasing molar ratios of ttsbi comonomer , the rigid polymer chain conformations become more irregular and randomly spiral , which reduce the chances for end - group encounters , finally preventing the formation of cyclics . all thdnpim were fully characterized by 1 h and 19 f nmr spectroscopy . the 1 h spectra of thdnpim - 50 ( fig1 ) were obviously similar to those of pim - 1 due to their identical ttsbi and tftpn monomers part . the additional signals due to the thdn monomer were easily assigned in 1 h . furthermore , the experimental ratio of intensity values for protons on the thdn aromatic rings compared with — ch 3 individually is exactly 10h : 12h ; as expected for two repeat units of the thdnpim - 50 copolymers . finally , the 19 f nmr spectra ( not shown ) were collected for all three polymers . no aromatic f signal was observed . thermal analyses results for the thdnpim series and pim - 1 are compared in table 8 . all the polymers are amorphous , remaining glassy up to their decomposition temperatures (& gt ; 430 ° c . ), and have excellent thermal stabilities . no glass transitions were detected up to temperatures of 350 ° c . actual onset temperatures of decomposition in nitrogen were in the range of 430 - 477 ° c . the dinaphthyl group imparts improved thermal stability , as shown by the increasing thermal stability with monomer molar ratio . the porosity of the polymers was probed by nitrogen sorption bet analysis at 77 k . the thdnpim were precipitated from chloroform into methanol , followed by extensive washing with methanol prior to sorption measurements . pim - 1 was tested under the same conditions and used as a reference material . nitrogen sorption measurements on these polymers revealed that samples were microporous . as shown in table 9 , the adsorption average pore width of thdnpim became slightly smaller with increasing molar content of thdn , with the exception of thdnpim - 100 , and bet data changed from 729 m 2 · g − 1 for pim - 1 to 560 m 2 · g − 1 through the copolymer series . the polymer chain packing can be calculated by fractional free volume ( ffv ), which is listed in table 9 [ bondi 1964 ; van krevelen 1990 ; chern 1987 ]. the calculated ffv values of thdnpim are almost identical to pim - 1 , though the density of pim - 1 is somewhat lower than those of the thdnpim series . since the amount of pore deformation during the adsorption process should be considered , the reason for the difference may be that the flexibility of the dinaphthyl bond is significantly higher than that of the spirobisindane bond . as the interfacial energy in a microporous system is rather high , this can result in elastic pore closure by deformation of the dinaphthyl bond during testing . thdnpim - 100 also shows good microporosity , but it consists mainly of cyclics and oligomers and is thus not suitable for comparison with the other polymers . in glassy or rubbery polymers , there is a trade - off relationship between gas permeability and selectivity for common gases . in general , higher permeability is gained at the cost of lower selectivity and vice versa . an upper bound performance for this trade - off relationship was proposed by robeson [ robeson 1991 ]. single gas permeability coefficients ( p ) were measured on polymer dense films of pim - 1 and thdnpim - 33 for o 2 , n 2 , he , h 2 , co 2 and a summary of these p values and ideal selectivities ( α ) for various gas pairs are shown in table 10 . thdnpim - 33 exhibited higher selectivity , coupled with some reduction in gas permeabilities , compared with pim - 1 . the overall permeability / selectivity performance combines to exceed the robeson upper bound line for o 2 / n 2 . from a material viewpoint , a shorter interchain distance imparts higher selectivity but lower permeability . in this case , thdn units shorten the distance between contorted centers , while maintaining a zig - zag structure , hence selectivity increased . molecular modeling analysis indicates that gas permeabilities for thdnpim - 33 were not excessively reduced , even though the thdn structure is more compact and has a shorter distance between contorted centers and smaller twist angle . fig1 shows that pim - 1 and thdnpim - 100 have similarly unperturbed zig - zag coil structures when viewed from ‘ x ’ and ‘ y ’ axes perspective . the angle at the spatially twisted dinaphthyl center in thdnpim - 100 ( approximately 60 °) is considerably smaller than that at the spirobisindane center in pim - 1 ( approximately 90 °). when both polymers are compared from the ‘ z ’ axis perspective , pim - 1 has an offset - linear conformation , whereas thdnpim - 100 has a zig - zag structure . this suggests that thdnpim - 100 is potentially even more contorted than pim - 1 , which could result in less efficient chain packing . the addition of thdn units into copolymers would also have the same effect . this is in good agreement with the gas permeability results . although the distance between the twisted dinaphthyl units is shorter and the kink angle is smaller than pim - 1 , there was little apparent change in the interchain spacing throughout the thdnpim copolymer series , as shown by ffv ( table 9 ). bet data shows that the surface area of the thdnpim - 33 copolymer is similar to pim - 1 , and as the molar content of thdn increases in the copolymer , surface area decreases . increasing the molar content of thdn also increases the amorphous nature of the copolymer , as shown by the disappearance of peaks in the x - ray diffraction measurements in fig1 . fig1 shows the gas permeability / selectivity trade - off plot for the o2 / n2 gas pair in relation to the robeson upper - bound . the v symbols show previous data reported by budd et al . and by staiger et al ., for pim - 1 . the data from budd et al . [ budd 2005b ] was reported at 200 mbar ( 2 . 90 psia ) feed pressure at 30 ° c . the data from staiger et al . [ staiger 2008 ] was reported at 4 atm ( 58 . 8 psia ) feed pressure 35 ° c . compared to data reported by budd et al . for films cast from tetrahydrofuran and measured at very low gas feed pressure , the oxygen permeability of chloroform - cast films of pim - 1 ( reaction for 120 min , high polydispersity material ) reported herein ( about 1 , 560 barrer ) is about 4 - times higher , but with a reduction in oxygen / nitrogen selectivity from 4 . 0 to 2 . 8 . also shown in fig1 is comparative pim - 1 data for pim - 1 produced at a reaction time of 40 min ( low polydispersity ). the disparity in results arises as the gas permeation properties of highly rigid glassy polymers depend strongly on film formation protocols , such as casting solvent type and drying conditions . as shown in table 10 and fig1 , the thdnpim - 33 copolymer , had an excellent combination of properties and was significantly more selective for gases / n 2 than pim - 1 . the selectivity coupled with high permeability combines to exceed the robeson upper - bound line for o 2 / n 2 . the results indicate that thdm can be incorporated as a comonomer for the synthesis of high molecular weight pims and tune gas permeability , selectivity and other properties of pim copolymers . preparation and characterization of pim ladder polymers containing disulfone - based monomers ( bspims ) this example focuses on the synthesis of new pims derived from sulfone monomers of example 3 . the effect of the sulfone side groups on microporosity for gas permeation behavior is investigated . the new pim copolymers were prepared from three different tetrafluoro disulfone monomers ( scheme 4 ), such that the resulting pim copolymer contains bulky , rigid groups . the disulfone - based pims present a new class of microporous polymers , and the structures , synthesis , physical properties , including the gas separations properties of this new class of pims are reported in this example . the synthesis of disulfone monomers comprised two steps : aromatic nucleophilic substitution reaction and oxidation . different from the known procedures [ kulka 1959 ; robson 1963 ; langille 1972 ], the sodium thiolate and pyridine mixture was added dropwise to hexafluorobenzene at − 20 ° c . instead of adding hexafluorobenezene into sodium thiolate and pyridine mixture at reflux temperature ( above 115 ° c .). hexafluorobenzene easily reacts with thiol groups under basic conditions by a aromatic nucleophilic substitution reaction , especially at an elevated temperature . even at room temperature , the addition of more than a two molar ratio of hexafluorobenzene to sodium thiolate still resulted in the formation of 1 , 4 - difluoroterathiobenzene compounds . according to the modified synthesis method , the side reactions were successfully avoided and three dithioether monomers were obtained in high yield . it was also found that the oxidation of thio groups was not complete by using excess h 2 o 2 in heterogeneous acetic acid suspension at 100 ° c . for 1 hour . after 1 hour oxidation , only 20 - 30 % thio groups were oxidized ( observed from 1 h nmr spectra ), which is different from the previous work [ robson 1963 ]. in general , the oxidation of dithio compounds is completed only after at least 24 h at 100 ° c . due to the poor solubility of partially oxidized compounds . tfbesb was oxidized without prior purification of the dithio compound , because the resulting disulfone monomer is more easily purified by recrystallization . in general , bspims - 100 , bspims - 50 and bspims - 33 were synthesized by copolymerization of ttsbi , tftpn , and disulfone monomers ( suffixes - 100 , - 50 , and - 33 refer to disulfone to ttsbi ratio , i . e . monomer molar ratios 1 : 0 : 1 ; 2 : 1 : 1 ; 3 : 2 : 1 ) using a procedure similar to that of pim - 1 in example 5 . thus , into a 100 ml three - necked flask equipped with a magnetic stirrer , an argon inlet , and a dean - stark trap , tftpn , ttsbi and disulfone monomers , anhydrous k 2 co 3 , dmac , and toluene were added . the mixture was refluxed at 160 ° c . for 40 - 60 min and the resulting viscous polymer solution was precipitated into methanol . a yellow flexible threadlike polymer was obtained . the polymer product was dissolved into chloroform and reprecipitated from methanol . the resulting polymer was refluxed for several hours with deionized water , and dried at 100 ° c . for 48 h . three series of ladder bspims containing disulfonyl groups and — cn groups were prepared via the snar polycondensation described above using various feed ratios of ttsbi / tftpn / disulfone monomers . the compositions and molecular weights of the polymers are listed in table 11 . the homopolymers are referred to as bspims - 100 and the copolymers are identified as bspims - 50 , and bspims - 33 , where pim stands for polymer of intrinsic microporosity , bs stands for disulfonyl groups , and 50 and 33 represents the percentage of disulfone monomer / ttsbi ( molar ratio ) in the copolymers . according to the polycondensation reaction mechanism for poly ( arylene ether ) s , high temperature and high concentration should be favorable for increasing the solubility of phenoxide salt and growing polymer chain , hence the appearance of cyclic oligomers and crosslinked structures could be effectively reduced . the polymerizations of pim - 1 and related pim copolymer structures ( tfmpspims ) are disclosed herein above using high monomer concentrations (& gt ; 25 % wt ) and at elevated temperatures ( e . g . 160 ° c .). excess toluene is introduced into the reaction not only to remove water , but also to provide solubility enhancement of the polymer . the reactions proceed smoothly and no evidence of crosslinking occurred . in contrast , the polycondensation of bspims of this example are different from pim - 1 and tfmpspims . according to the aromatic nucleophilic substitution reaction , there are two main factors influencing the substitution occurring in the aromatic system : ( i ) electronic activation and deactivation ; and , ( ii ) steric deactivation . in general , it can be assumed that every substituent ortho - to the substitution site has some steric effect on the reaction rate . however , for the majority of the data reported before , the electronic effect of the electron donating or withdrawing group appears to be far more pronounced than the steric effect [ bunnett 1951 ]. it is well known that electron withdrawing groups have different electronic activation , in the sequence of — so 2 r & gt ;— cf 3 & gt ;— cn [ march 1970 ]. because pims have a rigid ladder structure , which is different from linear flexible polymers , the steric deactivation effect may become important . in the first substitution reaction ( i ) shown in fig1 , wherein a phenoxide nucleophile displaces a fluorine atom , the steric effect may not be obvious because the electrophile can attack perpendicular to the ring . comparing three tetrafluoro - monomers , the initial substitution reactions will occur at the ortho - activated fluorine atom ( atom 1 ) near — so 2 r or — cn groups . when the second substitution reaction ( ii ) forms the dibenzodioxane - based structure , the ar - o — k + must attack the fluorine atom ( atom 2 ) on the same side , from the horizontal direction , resulting in a quasi - planar dioxane ring . therefore , the steric effects may become significant for dioxane ring formation in pims . if the electron withdrawing groups are not too sterically bulky , such as — cn and — cf 3 , the dibenzodioxane ring structure will be formed relatively easily . on the other hand , — so 2 r is large enough to prevent electrophilic attack efficiently from the horizontal direction . hence , under the high concentration reaction conditions used , after substitution reaction ( i ) occurs , there may be a competing substitution reaction ( i ) ( perpendicular direction ) on atom 1 of another monomer rather than the desired dibenzodioxane ring formation brought about by substitution reaction ( ii ) ( horizontal direction ) on atom 2 of the same monomer . however , if reaction conditions are used whereby the concentration of disulfone monomer is low , dibenzodioxane ring formation is more likely to occur after the initial substitution reaction ( i ) due to the dilution effect . meanwhile the reactivity of comonomer tftpn is not as high as the disulfone - based monomers . hence , with a progressively decreasing molar ratio of disulfone - based monomer to ttsbi , polydispersity is reduced , as observed by gpc . the gpc curves of bspims - 100 ( not shown ) reveal several shoulder peaks in the high molecular weight region along with the main peak . a minor gel fraction indicated that some crosslinking had occurred during the reaction . with decreasing ratios of disulfone - based monomers , only negligible gel formation was observed . the m n of all three bspims - 33 copolymers ( table 11 ) are above 41 , 000 da and the polydispersity indices are in the range of 2 - 5 . although the polydispersity indices of bspims - 33 are somewhat higher than typical pim - 1 and pstfpim obtained under the same conditions , the quality of the copolymers is still high enough to provide solution - cast robust free - standing films for gas permeability measurements . all three bspims - 50 were fully characterized by 1 h and 19 f nmr spectroscopy . the 1 h spectra of bspims - 50 were obviously similar to those of pim - 1 due to their identical ttsbi and tftpn monomer content . the additional signals due to the different disulfone monomer were easily assigned in 1 h nmr . furthermore , the experimental ratio of intensity values for aromatic protons h - 8 , 11 or 13 compared with aliphatic protons h - 2 , 3 was found to be exactly as expected ; for example , the spectra of the bspim - 50 displayed in fig1 all had proton ratios of exactly 4h : 8h per repeat unit . a three - dimensional representation of the pim polymer structures explains better what is observed in 1 h nmr spectroscopy . in 3 - d it is clear that one of the methyl groups is within very close proximity of h - 5 and therefore the electron cloud of the ch 3 group is shielding this proton , hence its very low chemical shift ( 6 . 4 ppm ) for an aromatic proton . from the h - 4 perspective , the two methyl groups are more distant , hence no shielding and the higher chemical shift ( 6 . 8 ppm ) is observed . this combines to explain why the methyl groups ( h - 1 ) do not appear as a singlet but as two singlets , because they are not equivalent in a 3 - d representation . the same principle also applies to h - 2 and h - 3 . those same h - 4 and h - 5 protons appear at the same position for both pim - 1 and bspim3 - 50 because the pendant groups , — cn and — so 2 ch 2 ch 3 respectively , are small and sufficiently distant from the aromatic protons that they have no effect on them . on the other hand , the two pim polymers bspim1 - 50 and bspim2 - 50 have bulky pendant phenyl groups with aromatic annular effects ( ring current ). these groups will cause h - 4 and h - 5 to appear at different chemical shifts . hence , multiple h - 4 and h - 5 signals appear for bspim1 - 50 and bspim2 - 50 but not for pim - 1 and bspim3 - 50 . the 19 f nmr spectra ( not shown ) were collected for all bspims homo - and copolymers . no aromatic f signal was observed . thermal analyses for bspims and pim - 1 were carried out and the results are summarized in table 12 . all polymers are amorphous and have no discernable t g up to their decomposition temperatures (& gt ; 317 ° c .). tga experiments showed that all polymers had excellent thermal stabilities and the actual onset temperature of decomposition in nitrogen ranged from 317 - 407 ° c . there was also some trend between the decomposition temperature and the monomer ratio . generally , polymers with — so 2 ar groups have high thermal stability . however , the — cn side group can enhance the thermal properties due to strong dipolar interactions . with increasing the molar ratios of — cn groups in the bspims , the onset of thermal decomposition also increased , as shown in table 12 . however , bspim homopolymers and copolymers all showed very good thermal stability even after the replacement of — cn with — so 2 r groups . waxd revealed that bspims - 100 were amorphous polymers . two main broad peaks were observed for all polymers ( fig1 ). according to bragg &# 39 ; s law , the peak representing 4 . 9 å might be attributed to chain - to - chain distance of space - efficiently packed chains . on the other hand , the second peak found at a d - spacing of approx . 6 . 5 å corresponds to more loosely packed polymer chains [ weber 2007 ]. as shown in fig1 , the d - spacing is 5 . 9 å for bspim2 and 6 . 5 å for pim - 1 . it becomes larger with decreasing size of disulfonyl groups in the main chain , suggesting that different disulfonyl groups affect polymer chain packing . the increasing size of disulfonyl groups leads to lower ffv due to inter - chain space filling . the fractional free volume ( ffv ) is calculated using the following equations : ffv =( v − v 0 )/ and v = m / ρ and v 0 = 1 . 3 v w where v is the total molar volume of the monomer unit ( cm 3 / mol ), m is the molar mass ( g / mol ) of the monomer unit and ρ is the density of the film ( g / cm 3 ), which is determined experimentally ( determined by measurements of the weight in air and in the ethanol ). v 0 is the volume occupied by the chains ( cm 3 / mol ). v 0 is assumed to be impermeable for diffusing gas molecules . v w is the van der waals volume calculated using the group contribution method of bondi [ bondi 1964 , van krevelen 1990 ; lee 1980 ]. according to bondi , a good approximation of relation between v 0 and v w is given by the last equation and the results are given in table 13 . the ffv varied from a minimum of 0 . 09 for bspim2 - 100 to a maximum of 0 . 26 for pim - 1 . the ffv of bspims - 33 is around 0 . 20 . compared to pim - 1 , bspims - 33 pack more efficiently . single - gas permeability coefficients ( p ) for o 2 , n 2 , co 2 were determined at 25 ° c . for dense polymer films ( pim - 1 , bspims - 33 ) and a summary of these p values and ideal selectivities for various gas pairs are shown in table 14 . in comparison with pim - 1 , the newly synthesized bspims - 33 exhibited higher selectivity , coupled with reductions in gas permeabilities . the selectivities for o 2 / n 2 and co 2 / n 2 were in the range of 3 . 7 - 4 . 2 and 16 - 23 , respectively . these results agree with the general tendency for gas permeation through polymer membranes , i . e . higher o 2 and co 2 permeability is gained at the cost of lower selectivity and vice versa . robeson proposed upper bound performance lines for this trade - off relationship between permeability and selectivity [ robeson 1991 ]. it is especially noteworthy that the o 2 permeation data of bspims - 33 were all positioned above robeson &# 39 ; s upper bound line . the high permeability and selectivity of o 2 and co 2 of the bspims - 33 polymers can be ascribed to the presence of both nitrile groups , which are sufficiently polar , and disulfone groups , which are bulky . while these pendant groups do not increase the ffv or reduce chain packing , they increase chain stiffness and likely have an effect of inter - chain space filling , which results in an increase in selectivity . on the other hand , the permeability decreases by enlarging the size of pendant groups on pims . the three disulfone groups have different effects on space filling and interchain packing . the permeability and selectivity of pims can be tuned by the size of pendant groups . for example , bspim3 - 33 has the best combination of permeability coupled with selectivity for o 2 / n 2 and co 2 / n 2 among the three bspims - 33 . molecular modeling analyses of bspims - 100 and pim - 1 with two repeat unit lengths were performed by using hyperchem ™ 7 . 0 software for studying the effect on geometry and steric interaction of disulfonyl groups on the polymer chains . in fig1 , a visual indication of major conformational changes in the polymers was obtained by the calculation results of geometry optimization with energy minimization using the amber method . the chains of pim - 1 with — cn pendant groups shown for comparison are relatively spiro - zigzag linear and regular ladder structure , which would lead to less chain packing . compared with pim - 1 , bspims showed a similarly unperturbed coil conformation . although disulfonyl groups are more bulky than the — cn group , they do not change the overall spiro - zigzag ladder chain structure and also do not take more intermolecular space . in addition the rigidity of the ladder polymers chain with disulfonyl groups can be enhanced by hindering bond distortions within the ladder chain , hence selective diffusion ability can be enhanced . the different pendant groups also act as the inter - chain space fillers with different size , which results in a decrease in permeability . the molecular modeling is in agreement with the gas permeability and selectivity data and help to explain the observed gas selectivity of bspims - 33 versus pim - 1 . preparation and characterization of pim ladder polymers containing 2 , 3 , 7 , 8 - tetrafluoro - 5 , 5 ′, 10 , 10 ′- tetraoxidethianthrene monomers ( totpims ) this example focuses on the synthesis of new pims derived from the 2 , 3 , 7 , 8 - tetrafluoro - 5 , 5 ′, 10 , 10 ′- tetraoxidethianthrene ( tftot ) monomer of example 4 . new pim copolymers ( designated totpims ) were prepared from the monomer in accordance with scheme 5 . the 2 , 3 , 7 , 8 - tetrafluoro - 5 , 5 ′, 10 , 10 ′- tetraoxidethianthrene ( tftot ) monomer is a novel compound . it is somewhat analogous to 2 , 3 , 7 , 8 - tetrachloro - 5 , 5 ′, 10 , 10 ′- tetraoxidethianthrene listed by mckeown [ mckeown 2006a ] but mckeown did not report any polymers made from the tetrachloro analogue . tftot has superior reactivity than the tetrachloro analogue , the tetrachloro analogue being a poor choice for polycondensation reactions . in general , totpims were synthesized by copolymerization of ttsbi , tftot and tftpn ( suffixes - 100 , - 66 , - 50 , - 33 , - 25 and - 20 refer to ttsbi : tftot : tftpn ratio , i . e . monomer molar ratios 1 : 1 : 0 , 3 : 2 : 1 , 2 : 1 : 1 , 3 : 1 : 2 , 4 : 1 : 3 and 5 : 1 : 4 , respectively ) using a procedure similar to that of pim - 1 in example 5 and as illustrated in scheme 5 . the homopolymer of ttsbi with tftot represented by totpim - 100 was not successfully isolated due to poor solubility of the polymer . thus , into a 100 ml three - necked flask equipped with a magnetic stirrer , an inert gas inlet , and a dean - stark trap , tftpn , ttsbi and tftot monomers , anhydrous k 2 co 3 , dmac and toluene were added . the mixture was refluxed at 160 ° c . for 40 - 60 min , and the resulting viscous polymer solution was precipitated into methanol . a yellow flexible threadlike polymer was obtained in most cases . the polymer product was dissolved into chloroform and reprecipitated from methanol . the resulting polymer was refluxed for several hours with deionized water , and dried at 100 ° c . for 48 h . molecular weights and monomer ratios are provided in table 15 . alsop d j , burdon j , tatlow j c . 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( 2002 ) macromolecules . 35 , 9513 - 9522 . other advantages that are inherent to the structure are obvious to one skilled in the art . the embodiments are described herein illustratively and are not meant to limit the scope of the invention as claimed . variations of the foregoing embodiments will be evident to a person of ordinary skill and are intended by the inventor to be encompassed by the following claims .