Patent Application: US-39420206-A

Abstract:
regioregular poly and other polythiophenes can be prepared by living polymerization which have good solubility , processability and environmental stability . the polymerization method can afford regioregular poly in high yields . kinetic study of polymerization revealed the living character of this process . the molecular weight of poly is a function of the molar ratio of the monomer to nickel initiator , and conducting polymers with relatively narrow molecular weight distribution are now readily available . sequential monomer addition resulted in new block copolymers containing different poly segments , which further confirms the “ livingness ” of this system . other synthetic methods can be used as well to conduct living polymerization . blends and electronic devices can be prepared .

Description:
priority u . s . provisional application ser . no . 60 / 667 , 065 filed apr . 1 , 2005 to mccullough et al ., is hereby incorporated by reference in its entirety . moreover , iovu et al ., macromolecules , 2005 , 38 , 8649 - 8656 , is hereby incorporated by reference including the experimental part , the figures , the results and discussion , and references and notes section . all references cited herein are hereby incorporated by reference in their entirety . the invention can encompass methods of making polymers , including block copolymers , as well as polymeric compositions , and compositions comprising block copolymers . for introduction , technical literature can be used in the practice of the present invention including the following . u . s . pat . no . 6 , 602 , 974 to mccullough et al . describes one system of block copolymers prepared by use of tailored endgroups and is incorporated by reference in its entirety including for its description of devices , synthetic methods , and block copolymers including both conductive and non - conductive segments . see also , liu et al ., macromolecules , 2002 , 35 , 9882 - 9889 ; liu et al ., angew . chem . int . ed ., 2002 , 41 , no . 2 , pages 329 - 332 , which are incorporated by reference in their entirety . these references also describe important morphological aspects of block copolymers including the formation of nanowires . u . s . pat . no . 6 , 166 , 172 to mccullough et al . describes an improved method for synthesis of conducting polymers ( grim methods ) including larger scale methods and is hereby incorporated by reference in its entirety . see also loewe et al ., macromolecules , 2001 , 34 , 4324 - 4333 which describes regioselectivity of these reactions . chemistry and applications for conductive polymers , as described herein , can be further found in for example ( i ) mccullough , adv . mater ., 1998 , no . 2 , pages 93 - 116 , ( ii ) mccullough et al ., handbook of conducting polymers , 2 nd ed ., 1998 , chapter 9 , pages 225 - 258 . in addition , electrically conductive polymers are described in the encyclopedia of polymer science and engineering , wiley , 1990 , pages 298 - 300 , including polyacetylene , poly ( p - phenylene ), poly ( p - phenylene sulfide ), polypyrrole , and polythiophene , which is hereby incorporated by reference in its entirety . this reference also describes blending and copolymerization of polymers , including block copolymer formation . polythiophenes are described , for example , in roncali , j ., chem . rev . 1992 , 92 , 711 ; schopf et al ., polythiophenes : electrically conductive polymers , springer : berlin , 1997 . polymeric semiconductors are described in , for example , “ organic transistor semiconductors ” by katz et al ., accounts of chemical research , vol . 34 , no . 5 , 2001 , page 359 including pages 365 - 367 , which is hereby incorporated by reference in its entirety . polymerization of polythiophenes and block copolymers for other types of non - thiophene polymers are described in , for example , yokozawa et al ., polymer journal , vol . 36 , no . 2 , pp . 65 - 83 ( 2004 ). block copolymers are generally known in the art . see for example yang ( ed . ), the chemistry ofnanostructured materials , 2003 , pages 317 - 327 (“ block copolymers in nanotechnology ”). also block copolymers are described in , for example , block copolymers , overview and critical survey , by noshay and mcgrath , academic press , 1977 . for example , this text describes a - b diblock copolymers ( chapter 5 ), a - b - a triblock copolymers ( chapter 6 ), and -( ab ) n - multiblock copolymers ( chapter 7 ), which can form the basis of block copolymer types in the present invention . additional block copolymers including polythiophenes are described in , for example , francois et al ., synth . met . 1995 , 69 , 463 - 466 , which is incorporated by reference in its entirety ; yang et al ., macromolecules 1993 , 26 , 1188 - 1190 ; widawski et al ., nature ( london ) , vol . 369 , jun . 2 , 1994 , 387 - 389 ; jenekhe et al ., science , 279 , mar . 20 , 1998 , 1903 - 1907 ; wang et al ., j . am . chem . soc . 2000 , 122 , 6855 - 6861 ; li et al ., macromolecules 1999 , 32 , 3034 - 3044 ; hempenius et al ., j am . chem . soc . 1998 , 120 , 2798 - 2804 . these and other references cited in this application can be used in the practice of the present invention . in addition , the block copolymers can comprise the conductive block , having conjugated structures which may or may not be doped , and the nonconductive block . the non - conductive block can include a variety of synthetic polymers including condensation , addition , and ring - opened polymers including for example , urethanes , polyamides , polyesters , polyethers , vinyl polymers , aromatic polymers , aliphatic polymers , heteroatom polymers , siloxanes , acrylates , methacrylates , phosphazene , silanes , and the like . inorganic and organic polymers can be used as the non - conductive part . if desired , the block copolymers can be blended with other components including inorganic glasses and metals as well as other polymers including inorganic polymers and organic polymers , as well as other conducting polymers either of the same type ( e . g ., two polythiophene types ) or of different type ( e . g ., a polythiophene with a nonpolythiophene ). the block copolymer can be used as a compatibilizing agent . the conducting polymer can be , for example , a polyacetylene , a polyphenylene , a polythiophene , a polyaniline , a polypyrrole , or a polyphenylene vinylene . in particular , the conducting polymer can be , for example , a polythiophene , optionally substituted at the 3 - position , at the 4 - position , or both . the conducting polymer can be , for example , a polythiophene with alkyl , aryl , alkoxy , aryloxy , ether , polyether , or heteroatomic subsituents . in particular , the conducting polymer can be a regioregular polythiophene , and more particularly , the conducting polymer can be a regioregular poly ( 3 - alkylthiophene ). the amount of regioregularity can be , for example , at least about 95 % or at least about 98 %. the conducting polymer can be a regioregular poly ( 3 - alkylthiophene ), in particular , wherein the alkyl group has 4 to 18 carbons , or alternatively , 4 to 12 carbons . the conducting polymer can be a copolymer including , for example , a random , gradient , or block copolymer . the conducting polymer can have a number average molecular weight of about 100 , 000 or less , or a number average molecular weight of about 50 , 000 or less , or alternatively , a number average molecular weight of about 25 , 000 or less , or alternatively , a number average molecular weight of about 10 , 000 or less , or alternatively , a number average molecular weight of about 5 , 000 or less . a variety of polymerization methods can be carried out in the present invention . for example , one embodiment is a method comprising : ( i ) combining a soluble thiophene monomer having a 3 - alkyl substituent with an amide base and a divalent metal halide to form a modified thiophene monomer ; and ( ii ) polymerizing the modified monomer at a first molar concentration [ m ] 0 in the presence of a transition metal complex polymerization initiator at a second molar concentration [ i ] under conditions to form regioregular poly ( 3 - alkylthiophene ), wherein at the start of polymerization the ratio of first molar concentration for monomer : second molar concentration for initiator is about 125 : 1 or less . the ratio can be , for example , 100 : 1 or less , 90 : 1 or less , 80 : 1 or less , 70 : 1 or less , 60 : 1 or less , or 50 : 1 or less . if desired , the method can further comprise chain extending the regioregular poly ( 3 - alkylthiophene ) with addition of a second thiophene monomer to form an ab block copolymer . another embodiment is a method comprising : ( i ) combining a soluble thiophene monomer having a 3 - substituent with an amide base and a divalent metal halide to form a modified thiophene monomer having a 3 - substituent , ( ii ) polymerizing the modified monomer at a first molar concentration [ m ] 0 in the presence of a transition metal complex polymerization initiator at a second molar concentration [ i ] under conditions to form regioregular polythiophene having a 3 - substituent , wherein the polymerization is carried out under conditions which provides a degree of polymerization which can be substantially predicted based on the first and second molar concentrations . still further , another embodiment is a method comprising : ( i ) polymerizing a first thiophene monomer by grignard metathesis polymerization to form a polythiophene intermediate under conditions which provide for living polymerization , ( ii ) chain extending the intermediate with addition of a second thiophene monomer to form an ab block copolymer . the polymerization can be carried out at about 0 ° to about 50 ° c ., or alternatively , at about 10 ° to about 40 ° c . the initiator can comprise an organometallic compound or a transition metal complex . for example , the initiator can be a nickel , platinum , or palladium compound . nickel ( ii ) complexes can be used . the intiator , for example , can be a nickel ( ii ) diphosphinohalogeno complex . in a preferred embodiment , the conducting polymer is a polythiophene and the initiator is an organometallic compound or a transition metal complex . in another preferred embodiment , the conducting polymer is a regioregular polythiophene and the initiator is a nickel compound . in another preferred embodiment , the conducting polymer is a polythiophene having a number average molecular weight of about 50 , 000 or less and the initiator is an transition metal compound . another embodiment comprises a regioregular polythiophene substituted in the 3 - position and having a number average molecular weight of about 10 , 000 or less and the initiator is an organometallic nickel ( ii ) compound . the first molar concentration can be about 1 m or less , or alternatively , about 0 . 5 m or less , or alternatively , about 0 . 1 m or less . preferably , the polymerizing provides regioregular poly ( 3 - alkylthiophene ). preferably , the polymerizing provides regioregular poly ( 3 - alkylthiophene ), wherein the ratio is about 80 : 1 or less , wherein the first molar concentration is about 1 m or less , and wherein the initiator is a nickel ( ii ) complex . preferably , the polymerizing can provide regioregular poly ( 3 - alkylthiophene ), wherein the ratio is about 50 : 1 or less , wherein the alkyl group comprises 4 to 12 carbons , and wherein the first molar concentration is about 0 . 5 m or less . preferably , the polymerizing also provides regioregular poly ( 3 - alkylthiophene ), wherein the ratio is about 50 : 1 or less , wherein the first molar concentration is about 0 . 5 m or less , and wherein the initiator is a nickel ( ii ) complex . preferably , the polymerizing is carried out at a temperature of about 0 ° c . to about 50 ° c ., wherein the initiator is a nickel ( ii ) complex , and wherein the alkyl group comprises 4 to 18 carbons . preferably , the first molar concentration is about 0 . 5 m or less , wherein the ratio is about 100 : 1 or less , and wherein the initiator is a ni ( ii ) diphosphinohalogen complex . preferably , the ratio is about 50 : 1 or less , wherein the first molar concentration is about 0 . 1 or less , and wherein the initiator is a nickel ( ii ) complex . preferably , the ratio is about 50 : 1 or less , wherein the first molar concentration is about 0 . 1 or less , wherein the initiator is a nickel ( ii ) diphosphinohalogen complex , wherein the alkyl group comprises 4 to 12 carbons , and wherein the polymerizing is carried out at a temperature of about 10 ° c . to about 40 ° c . another embodiment is a method comprising : polymerizing 3 - alkylthiophene monomer by grignard metathesis polymerization at a first molar concentration [ m ] 0 in the presence of an organometallic polymerization initiator at a second molar concentration [ i ] under conditions to form regioregular poly ( 3 - alkylthiophene ), wherein the polymerization is carried out under conditions which provides a degree of polymerization which can be predicted based on the first and second molar concentrations . this can be followed by chain extension . preferably , the alkyl group comprises 4 to 18 carbons , or alternatively , 4 to 12 carbons . preferably , the polymerizing is carried out at a temperature of about 0 ° c . to about 50 ° c . preferably , the ratio [ m ] 0 :[ i ] is about 136 : 1 or less . preferably , the first molar concentration is about 1 m or less . preferably , the initiator is a nickel ( ii ) complex . preferably , the polymerizing provides regioregular poly ( 3 - alkylthiophene ). preferably , the polymerizing provides regioregular poly ( 3 - alkylthiophene ), wherein the initiator is a nickel ( ii ) diphosphinohalogen complex , wherein the ratio [ m ] 0 :[ i ] is about 80 : 1 or less , and wherein the first molar concentration is about 0 . 5 m or less . preferably , the polymerizing provides regioregular poly ( 3 - alkylthiophene ), wherein the alkyl group comprises 4 to 12 carbons , wherein the polymerizing is carried out at a temperature of about 10 ° c . to about 40 ° c ., and wherein the initator is a nickel ( ii ) complex . preferably , the polymerizing provides regioregular poly ( 3 - alkylthiophene ), wherein the first molar concentration is about 0 . 1 m or less and the ratio [ m ] 0 :[ i ] is about 50 : 1 or less , and the polymerizing is carried out at a temperature of about 10 ° c . to about 40 ° c . another embodiment is a method comprising : polymerizing a thiophene monomer by grignard metathesis polymerization under conditions which provide for living polymerization , wherein the thiophene monomer is optionally substituted at the 3 - position , the 4 - position , or both . the polymer can be chain extended . preferably , the conditions comprise 3 - alkylthiophene monomer at a first molar concentration [ m ] 0 in the presence of an organometallic polymerization initiator at a second molar concentration [ i ] under conditions to form regioregular poly ( 3 - alkylthiophene ), wherein at the start of polymerization the ratio [ m ] 0 :[ i ] is about 136 : 1 or less . preferably , the conditions comprise 3 - alkylthiophene monomer at a first molar concentration [ m ] 0 in the presence of a transition metal complex polymerization initiator at a second molar concentration [ i ] under conditions to form regioregular poly ( 3 - alkylthiophene ), wherein the polymerization provides a degree of polymerization which can be predicted based on the first and second molar concentrations . preferably , the conditions comprise use of a nickel ( ii ) initiator . preferably , the conditions comprise polymerizing at about 0 ° c . to about 50 ° c . preferably , the conditions comprise an initial concentration of monomer of about 1 m or less . preferably , the conditions comprise use of a nickel ( ii ) initiator , polymerizing at about 0 ° c . to about 50 ° c ., and an initial concentration of monomer of about 1 m or less . preferably , the alkyl group comprises 4 to 18 carbons . preferably , the polymerizing provides regioregular poly ( 3 - alkylthiophene ). preferably , the polymerizing provides regioregular poly ( 3 - alkylthiophene ), wherein the conditions comprise use of a nickel ( ii ) initiator , polymerizing at about 10 ° c . to about 40 ° c ., and an initial concentration of monomer of about 1 m or less , and wherein the alkyl group comprises 4 to 12 carbons . another embodiment is a method comprising : polymerizing a first thiophene monomer by grignard metathesis polymerization to form a polythiophene intermediate under conditions which provide for living polymerization , and chain extending the intermediate with addition of a second thiophene monomer to form an ab block copolymer . preferably , the method provides further chain extending the ab block copolymer with a third thiophene monomer which optionally is the same as the first thiophene monomer . preferably , the method further provides chain extending the ab block copolymer to form an aba copolymer . preferably , the first thiophene monomer , the second thiophene monomer , or both are substituted at the 3 - position , the 4 - position , or both . preferably , the method further comprises the steps of chain extension to form abc block copolymer . preferably , the first thiophene monomer , the second thiophene monomer , or both are substituted in the 3 - position , the 4 - position , or both . preferably , the polymerizing is carried out with a initial monomer : initiator molar ratio of about 140 : 1 or less . preferably , the polymerizing is carried out with an initial monomer : initiator molar ratio of about 80 : 1 or less . preferably , the polymerizing is carried out at about 0 ° c . to about 50 ° c ., and wherein the ab block copolymer is a regioregular polythiophene block copolymer . preferably , the ab block copolymer is a regioregular polythiophene block copolymer . another embodiment is a composition comprising : an ab block copolymer , wherein the a block is a regioregular polythiophene , and the b block is also a regioregular polythiophene . the regioregular polythiophene can be , for example , at least 90 % regioregular , or at least 95 % regioregular , or at least 98 % regioregular . preferably , the a block and / or the b block regioregular polythiophene is substituted at the 3 - position , at the 4 - position , or both . preferably , the a block and / or the b block regioregular polythiophene is substituted at the 3 - position . preferably , the a block and / or the b block regioregular polythiophene is substituted at the 4 - position . preferably , the a block and / or the b block regioregular polythiophene is substituted at the 3 - position and the 4 - position . preferably , the ab block copolymer has a number average molecular weight of about 25 , 000 or less . preferably , the ab block copolymer has a polydispersity of about 2 . 0 or less . preferably , the ab block copolymer has a polydispersity of about 1 . 5 or less . preferably , the ab block copolymer is soluble , including soluble in organic solvents . preferably , the ab block copolymer is soluble , wherein the ab block copolymer has a number average molecular weight of about 25 , 000 or less , and wherein the ab block copolymer has a polydispersity of about 1 . 5 or less . preferably , the a block and / or the b block regioregular polythiophene is substituted at the 3 - position , at the 4 - position , or both , and wherein the ab block copolymer is soluble , wherein the ab block copolymer has a number average molecular weight of about 25 , 000 or less , and wnerein the ab block copolymer has a polydispersity of about 1 . 5 or less . another embodiment is a composition comprising : an aba block copolymer , wherein the a block is a regioregular polythiophene and the b block is also a regioregular polythiophene . preferably , the a block and / or the b block regioregular polythiophene is substituted at the 3 - position , at the 4 - position , or both . preferably , the a block and / or the b block regioregular polythiophene is substituted at the 3 - position . preferably , the a block and / or the b block regioregular polythiophene is substituted at the 4 - position . preferably , the a block and / or the b block regioregular polythiophene is substituted at the 3 - position and the 4 - position . preferably , the ab block copolymer has a number average molecular weight of about 25 , 000 or less . preferably , the ab block copolymer has a polydispersity of about 1 . 5 or less . preferably , the ab block copolymer is soluble . preferably , the ab block copolymer is soluble , wherein the ab block copolymer has a number average molecular weight of about 25 , 000 or less , and wherein the ab block copolymer has a polydispersity of about 1 . 5 or less . preferably , the a block and / or the b block regioregular polythiophene is substituted at the 3 - position , at the 4 - position , or both , and wherein the ab block copolymer is soluble , wherein the ab block copolymer has a number average molecular weight of about 25 , 000 or less , and wherein the ab block copolymer has a polydispersity of about 1 . 5 or less . another embodiment is a composition comprising : an abc block copolymer , wherein the a block is a regioregular polythiophene , wherein the b block is also a regioregular polythiophene , and wherein the c block is also a regioregular polythiophene . the polymers can be used in doped or undoped form . doping can be ambient doping . doping can be controlled to vary conductivity from insulating , to semiconductive , to fully conductive . doping time can be varied to provide the desired doping level . conductivities greater than 10 − 5 s / cm can be achieved . if desired , conductivities greater than 10 s / cm can be achieved . the amount of block copolymer non - conductive component , and / or the amount of non - conductive blend component can be varied to help control conductivity and provide suitable balance of conductivity and material properties for a given application . the applications of these materials are not particularly limited but include optical , electronic , energy , biomaterials , semiconducting , electroluminescent , photovoltaic , leds , oleds , pleds , sensors , transistors , field effect transistors , batteries , flat screen displays , organic lighting , printed electronics , nonlinear optical materials , dimmable windows , rfid tags , fuel cells , and others . see for example kraft et al ., angew . chem . int ed ., 1998 , 37 , 402 - 428 and discussion of applications which is hereby incorporated by reference in its entirety . see also , shinar , organic light - emitting devices , springer - verlag , 2004 . see also &# 39 ; 974 patent noted above . hole - injection layers can be fabricated . multilayer structures can be fabricated and thin film devices made . thin films can be printed . patterning can be carried out . printing on consumer products can be carried out . small transistors can be fabricated . in many applications , the composition is formulated to provide good solution processing and thin film formation . blends with other polymers including conductive polymers can be prepared . the nanowire morphology of the block copolymers can be exploited in nanoscale fabrication . the invention is further described with use of the following non - limiting working examples including also a description of polymerization mechanism and examination thereof with use of working examples . nickel - initiated cross - coupling polymerization of thiophenes can proceed via a chain - growth mechanism . 27 , 28 in particular , the reference to sheina , e . e . ; liu , j . ; iovu , m . c . ; laird , d . w . ; mccullough , r . d . macromolecules 2004 , 37 , 3526 - 3528 is incorporated by reference in its entirety including the figures , the experimental section , citations to references , and the supplementary material . furthermore , if desired , the addition of various grignard reagents ( r ′ mgx ) at the end of polymerization can result in the end - capping of regioregular pats with an r ′ end group . 29 the sheina et al . macromolecules paper describes the mechanism of the nickel initiated cross - coupling polymerization for the synthesis of regioregular poly ( 3 - alkylthiophene ) ( see fig2 ). 27 a simplified reaction scheme also is given here ( fig1 ). treatment of 2 , 5 - dibromo - 3 - alkylthiophene with 1 equiv of rmgcl ( r = alkyl ) results in magnesium - bromine exchange reaction , also referred as grignard metathesis ( grim ) ( fig1 ). this reaction proceeds with a moderate degree of regioselectivity leading to a distribution of regiochemical isomers ( 1 ) and ( 1 ′) of 85 : 15 to 75 : 25 . the gc - ms analysis after the addition of ni ( dppp ) cl 2 indicated that only isomer ( 1 ) is incorporated into the polymer , while isomer ( 1 ′) was not consumed . the first step in the mechanism is the reaction of 2 equiv of 2 - bromo - 5 - chloromagnesium - 3 - alkylthiophene monomer ( 1 ) with ni ( dppp ) cl 2 generating a bis - organonickel compound , which undergoes reductive elimination resulting in the formation of an associated pair of the 5 , 5 ′- dibromobithienyl ( tail - to - tail coupling ) and ni ( 0 ). it is proposed that the associated pair is formed as a result of the coordination of 1 , 3 - bis ( diphenylphosphino ) propane nickel ( 0 ) to the thiophene ring in η 2 or η 4 bonded fashion . similar type of ni ( 0 )- η 2 arene complexes were previously reported . 33 - 35 the dimer undergoes fast oxidative addition to the nickel ( 0 ) center generating a new organonickel compound . growth of the polymer chain occurs by insertion of one monomer at a time , where the ni ( dppp ) moiety is incorporated into polymer chain as an end group ( compound 2 in fig1 ). according to the proposed mechanism only one structural defect ( one tail - to - tail coupling ) per polymer chain is generated during the proposed catalytic cycle . first , a kinetic study of the grignard metathesis method for the synthesis of regioregular poly ( 3 - hexylthiophene ) is described . the experimental results can be used to demonstrate the “ living ” nature of this polymerization . in the case of grignard metathesis method , poly ( 3 - alkylthiophenes ) with relatively high molecular weight were formed almost immediately . this observation was in contradiction with the generally accepted step growth polymerization mechanism proposed for nickel - catalyzed cross - coupling polymerization , where one would expect the fast disappearance of the monomer and increase of the molecular weight toward the end the reaction . several experiments were performed at various ni ( dppp ) cl 2 concentrations with a constant monomer ( 1 ) concentration . the reaction rates increased with the increase in the ni ( dppp ) cl 2 concentration as shown in fig2 . the linearity of the semilogarithmic kinetic plots was observed only up to ˜ 40 % conversion . the non - linearity in the semilogarithmic kinetic plots would indicate the presence of termination reactions , which could be due to the aggregation of polymer chains . 36 if the reaction medium becomes heterogeneous due to the formation of polymer aggregates the active centers are not accessible for further insertion of the monomer . due to the non - linearity of the semilogarithmic kinetic plots , the system can be regarded as a non - optimized “ living ” or “ quasi - living ” polymerization . further optimization in the reaction conditions can provide a better “ living ” grim polymerization . molecular weight vs conversion plot ( fig3 ) and the gpc traces ( fig4 ) show the increase of molecular weight with conversion , which supports a quasi -“ living ” chain growth mechanism for nickel - initiated cross - coupling polymerization . the molecular weight of the polymers is a function of the molar ratio of monomer ( 1 ) to ni ( dppp ) cl 2 initiator ( fig3 ). furthermore the number average molecular weight of the polymers can be predicted by the formula : dp n = δ ⁡ [ m ] t [ ni ⁡ ( dppp ) ⁢ cl 2 ] 0 accordingly to the proposed mechanism ni ( dppp ) cl 2 acts as an initiator rather than a catalyst , and ni ( dppp ) moiety is incorporated in polymer as an end group ( polymer 2 , fig1 ). poly ( 3 - hexylthiophenes ) with relatively narrow polydispersities ( pdi & lt ; 1 . 5 ) were obtained for the experiments performed at high concentrations of ni ( dppp ) cl 2 ( fig3 ). to complement the previous experiments , another series of experiments were conducted at a constant ni ( dppp ) cl 2 concentration , while varying the 2 - bromo - 5 - chloromagnesium - 3 - hexylthiophene ( monomer ) concentration . the polymerizations were conducted at low temperatures ( 0 - 2 ° c .) to slow the rate of reaction and conserve the linearity of the semilogarithmic kinetic plots . the later allowed for a more accurate determination of the initial polymerization rate . the reaction rates increased with the increase in the monomer concentration as shown in fig5 . molecular weight vs conversion plot ( fig6 ) also shows the increase of molecular weight with conversion and poly ( 3 - hexylthiophene ) with relatively narrow polydispersities ( pdi & lt ; 1 . 5 ) were synthesized . a value of ˜ 1 for the reaction order with respect to the monomer was obtained from the slope of the plot of the logarithm of the initial rate of polymerization vs . the logarithm of the monomer concentration ( fig7 ). grignard metathesis method for the synthesis of regioregular poly ( 3 - alkylthiophenes ) results in the formation of regioregular polymers (˜ 98 % head - to - tail couplings ). quenching of nickel terminated poly ( 3 - alkylthiophene ) ( polymer 2 , fig1 ) with water / hcl mixture results in the formation of h / br terminated polymer . as an example , the full 500 mhz 1 h nmr spectrum of a moderate molecular weight regioregular poly ( 3 - hexylthiophene ) ( rr - pht ) is presented in fig9 . the main absorption signals of rr - pht are assigned as shown . two small triplets at δ ˜ 2 . 6 ppm of the same intensity for h / br terminated rr - pht can be assigned to the methylene protons on the first carbon substituent ( h and h ′) on the end units . furthermore , the appearance of the two separate triplet signals at different resonance frequencies is due to different chemical environment around h and h ′ ( fig9 ( c )). when the h / br terminated polymer is subjected to a magnesium halogen exchange reaction ( fig8 ) and quenched with an acidic methanol / water mixture , a pristine h / h terminated rr - pht is formed . consequently , the signal generated by the methylene protons h ′ is shifted down field with the two groups ( h and h ′) resonating at the same frequency ( fig9 ( b )). the integration values from 1 h nmr ( 500 mhz ) spectrum of rr - pht - h / br and rr - pht - h / h terminated polymers are presented in table 1 . the intensity of the h peak is doubled in the absence of the bromine atom relative to the main peak ( b ) of first β - substituent methylene protons . these observations indicate that nmr analysis cannot distinguish between the two different types of coupling ( e . g ., head - to - tail ( ht ) and tail - to - tail ( tt )), when rr - pht h / h terminated contains only one structural defect per polymer chain . however , it allows a relatively accurate determination of molecular weight from the integration of end - group resonances relative to the bulk polymer . for instance , dp n for the aforementioned polymer equals to the ratio of b to h and results in 50 monomer units corresponding to m n = 8 , 300 . a previous report showed that the addition of various grignards reagents to the nickel - terminated poly ( 3 - alkylthiophene ) results in the formation of end - functional polymers . [ 29 ] the addition of a new portion of 2 - bromo - 5 - chloromagnesium - 3 - alkylthiophene monomer at the end of the polymerization resulted in the further increase of the molecular weight of the final polymer . both experiments indicate the “ living ” nature of the nickel terminated poly ( 3 - alkylthiophene ). the main focus of this section is the chain extension of rr - pats through sequential addition of a different monomer . an example of chain extension is based on the synthesis of poly ( 3 - hexylthiophene )- b - poly ( 3 - dodecylthiophene ) ( pht - b - pddt ) block copolymer and is described herein for the first time . the synthetic strategy used for the synthesis of pht - b - pddt is outlined in fig1 . the first step involves preparation of rr - pht with well - defined end group and structural homogeneity . the reaction parameters were chosen with a special consideration with respect to the monomer ( 2 , 5 - dibromo - 3 - hexylthiophene ) concentration ( e . g ., [ ht ] 0 = 0 . 02 mol / l ). higher dilutions are preferable to insure an easier access to the active centers and to avoid possible precipitation of the resultant polymer . the second step of the reaction is preparation of 2 - bromo - 5 - chloromagnesium - 3 - dodecylthiophene using grignard metathesis . this reaction generates a mixture of regiochemical isomers with a typical distribution in the range of 75 : 25 to 85 : 15 . the 5 - bromo - 2 - chloromagnesium - 3 - dodecylthiophene does not participate in the catalytic cycle due to the sterically hindered 2 - position . the reaction was relatively fast and very efficient , reaching 90 % conversion in less than 3 hours , at room temperature . the molecular weight versus conversion plot ( fig1 ) and the gpc traces ( fig1 ) showed an increase of molecular weight with conversion , which strongly supported the chain extension through “ living ” intermediates . the low molecular weight tailing observed in the gpc trace of pht - b - pddt indicates the formation of some dead or inactive chains during the chain extension process . the successive monomer insertion into the second block was monitored by 1 h nmr . the full 1 h nmr spectra of the initial rr - pht homopolymer and the resultant di - block copolymer are represented in fig1 . the main resonance frequencies were assigned as shown . fig1 illustrates the progressive incorporation of pddt block into copolymer ( the intensity of g ′ protons increases as the molecular weight of the pddt block increases ). the resultant copolymer was readily soluble in common organic solvents ( e . g ., chloroform , toluene , 1 , 2 , 4 - trichlorobenzene , thf ) and possessed excellent film - forming abilities . the uv - vis spectra of the poly ( 3 - hexylthiophene )- b - poly ( 3 - dodecylthiophene ) ( fig1 ) in the solid state indicates the vibrational structure with well - defined peaks ( e . g . λ max = 558 nm and the lower intensity peaks at λ = 524 and 607 nm ). synthesis of poly ( 3 - dodecylthiophene )- b - polytiophene - b - poly ( 3 - dodecylthiophene ) tri - block copolymer was performed in a similar manner . the length of polythiophene block was carefully chosen due to its very poor solubility . the shift in the gpc traces indicates the formation of the block copolymer ( fig1 ). however the low molecular weight tailing in the gpc traces indicates the presence of some dead or inactive chains during the chain extension process . the low solubility of the poly ( 3 - dodecylthiophene )- b - polythiophene could cause the precipitation of the nickel - terminated polymer resulting in the loss of the activity towards further monomer insertion . this could be prevented by the use of higher dilutions or lowering the polythiophene content . the uv - vis spectra of poly ( 3 - dodecylthiophene ) precursor and poly ( 3 - dodecylthiophene )- b - polythiophene - b - poly ( 3 - dodecylthiophene ) ( fig1 ) films shows a bathochromic shift as compared with the solution . the films of poly ( 3 - hexylthiophene )- b - poly ( 3 - dodecylthiophene ) ( pht - b - pddt ) and poly ( 3 - dodecylthiophene )- b - polythiophene - b - poly ( 3 - dodecylthiophene ) ( pddt - b - pt - b - pddt ) exhibited relatively good electrical conductivities . as illustrated in fig1 , the conductivity increased proportionally with doping times . fig1 and 20 provide sem images of the block copolymer thin films . fig1 provides an sem image of pht - b - pddt film ( drop cast from toluene solution ; conc = 5 mg / ml ; film thickness = 1 . 67 μm ). fig2 provides an sem image of pddt - b - pt - b - pddt film ( drop cast from toluene solution ; conc = 5 mg / ml ; film thickness = 0 . 698 μm ). synthesis of 2 , 5 - dibromo - 3 - hexylthiophene and 2 , 5 - dibromo - 3 - dodecylthiophene were performed according to the literature . 13 , 14 thf was dried over k / benzophenone and freshly distilled prior to use . [ 1 , 3 - bis ( diphenylphosphino ) propane ]- dichloronickel ( ii ) ( ni ( dppp ) cl 2 ), alkyl magnesium chloride ( 2m in diethyl ether ) and p - dimethoxybenzene were purchased from aldrich chemical co ., inc . and used without further purification . in a typical experiment , a dry 100 ml three - neck round bottom flask was flashed with n 2 and was charged with 2 , 5 - dibromo - 3 - hexylthiophene ( 1 . 6 g , 5 mmol ), p - dimethoxybenzene ( internal standard ) ( 0 . 2 g ), and anhydrous thf ( 50 ml ). a 2m solution of alkyl magnesium chloride ( 2 . 5 ml , 5 mmol ) in diethyl ether ( et 2 o ) was added via a deoxygenated syringe , and the reaction mixture was gently refluxed for 2 hrs . at this time an aliquot ( 0 . 5 ml ) was taken out and quenched with water . the organic phase was extracted in et 2 o and subjected to gc - ms analysis to determine the composition of the reaction mixture . the main components of the reaction mixture were 2 - bromo - 5 - chloromagnesium - 3 - hexylthiophene and 5 - bromo - 2 - chloromagnesium - 3 - hexylthiophene regioisomers . usually less than 5 % of unreacted 2 , 5 - dibromo - 3 - hexylthiophene was detected by gc - ms analysis . the concentration of 2 - bromo - 5 - chloromagnesium - 3 - hexylthiophene isomer was considered as the initial monomer concentration . the oil bath was then removed and the reaction mixture was allowed to cool down to 23 - 25 ° c ., at which time ni ( dppp ) cl 2 ( 0 . 04 g , 0 . 075 mmol ) was added as a suspension in 1 ml of anhydrous thf . after addition of ni ( dppp ) cl 2 , aliquots ( 1 ml ) were taken at different time intervals and each was precipitated in methanol ( 5 ml ). for each aliquot a sample was prepared in et 2 o ( 2 ml ) and subjected to gc - ms analysis for the determination of concentration of unreacted monomer . after filtration through ptfe filters ( 0 . 45 μm ), the molecular weight of the pristine polymer samples was measured by gpc . a dry 250 ml three - neck round bottom flask ( a ) was charged with 2 , 5 - dibromo - 3 - hexylthiophene ( 1 . 6 g , 5 mmol ), p - dimethoxybenzene ( internal standard ) ( 0 . 3 g ) and anhydrous thf ( 165 ml ). a 2m solution of alkyl magnesium chloride ( 2 . 5 ml , 5 mmol ) in diethyl ether ( et 2 o ) was added via a deoxygenated syringe , and the reaction mixture was gently refluxed for 2 hrs . after the consumption of 2 , 5 - dibromo - 3 - hexylthiophene the reaction mixture was cooled at 20 - 22 ° c . the concentration of unreacted 2 - bromo - 5 - chloromagnesium - 3 - hexylthiophene was determined by gc - ms ( more than 90 % of monomer was consumed in 2 hrs ). ni ( dppp ) cl 2 ( 0 . 05 g , 0 . 1 mmol ) was added as a suspension in 1 ml of anhydrous thf . the polymerization continued for 3 hrs before addition of 2 - bromo - 5 - chloromagnesium - 3 - dodecylthiophene ( prepared as described below ). a dry 50 ml three - neck round bottom flask ( b ) flashed with n 2 was charged with 2 , 5 - dibromo - 3 - dodecylthiophene ( 4 . 1 g , 10 mmol ) and anhydrous thf ( 10 ml ). a 2m solution of alkyl magnesium chloride ( 5 ml , 10 mmol ) in diethyl ether ( et 2 o ) was added via a deoxygenated syringe , and the reaction mixture was gently refluxed for 2 hrs . the concentration of 2 - bromo - 5 - chloromagnesium - 3 - dodecylthiophene was determined by gc - ms . gc - ms analysis was performed on a hewlett - packard agilent 6890 - 5973 gc - ms workstation . the gc column was a hewlett - packard fused silica capillary column cross - linked with 5 % phenylmethyl siloxane . helium was the carrier gas ( 1 ml / min ). the following conditions were used for all gc - ms analyses : injector temperature , 250 ° c . ; initial temperature , 70 ° c . ; temperature ramp , 10 ° c ./ min ; final temperature , 300 ° c . gpc measurements were performed on a waters 2690 separations module apparatus and a waters 2487 dual λ absorbance detector with chloroform as the eluent ( flow rate 1 ml / min , 35 ° c ., λ = 254 nm ) and a series of three styragel columns ( 10 4 , 500 , 100 å ; polymer standard services ). toluene was used as an internal standard and calibration based on polystyrene standards was applied for determination of molecular weights . 1 h nmr spectra of the polymer solutions in cdcl 3 were recorded on a bruker avance 500 mhz spectrometer . uv - vis - nir spectra were measured on polymer solutions in anhydrous chloroform or polymer thin films cast onto 22 mm square cover glass using a uv - vis - nir spectrophotometer varian cary 5000 . electrical conductivity measurements were performed by a standard spring - loaded pressure contact signatone s - 301 - 4 four point probe , which was connected to a hewlett - packard 6632a system dc power supply , a hewlett packard 3457 a multimeter ( for voltage measurements ), and a keithley model 196 system dmm ( for current measurements ). thin polymer films cast onto glass were chemically oxidized by exposure to iodine vapors for various periods of time . the films were obtained from drop cast solutions of the polymer in dry toluene ( 5 mg ml − 1 ). the film thickness ( cross - section ) was measured by scanning electron microscopy ( sem ) using a hitachi s - 2460n electron microscope . a model experiment was first carried out . in a cross - coupling step polymerization catalyzed by ni ( dppp ) cl2 , one would expect a fast disappearance of the monomer and increase of the polymer molecular weight toward the end of the polymerization . on the basis of experimental results , it was observed that relatively high molecular weight polymer forms almost immediately . as a model reaction , it was also found that 2 equiv of a variety of aryl dibromides and 1 equiv of an aryl organometallic ( either magnesium or zinc ) gives a near quantitative yield of the trimeric aryl and minor amounts (& lt ; 1 %), if any , of the dimer . these results indicate the very strong preference of the ni ( 0 ) ( see fig2 , intermediate 3 ) to form a nondiffusive associated pair , resulting in near 100 % formation of the trimer . the results indicate that the polymerization proceeds with selective oxidation addition to the growing 2 - bromopolythiophene and that these regioregular polymerizations progress by a chain growth mechanism rather than a step growth . a typical example is when a 0 . 1 m solution of thiophene ( 0 . 42 g , 5 mmol ) or 2 - methylthiophene ( 0 . 49 g , 5 mmol ) in anhydrous thf ( 50 ml ) cooled to − 40 ° c . ( acetonitrile / dry ice bath ) was charged with a dropwise addition of n - butyllithium ( 2 ml , 5 mmol ) via a syringe . after stirring the reaction mixture for 40 min at − 40 ° c ., anhydrous zncl 2 ( 0 . 7 g , 5 mmol ) was added in one portion , and the stirring continued for another 15 min . the cooling bath was removed , and the reaction mixture was allowed to warm to rt , at which point the reaction mixture was transferred to a different reaction flask charged with 10 mmol an appropriate dibromoaryl compound ( e . g ., 2 , 5 - dibromo - 3 - methylthiophene , 2 , 5 - dibromothiophene , or 1 , 4 - dibromo - benzene ) and 0 . 05 mmol of [ 1 , 3 - bis ( diphenylphosphino )- propane ] dichloronickel ( ii ) ( ni ( dppp ) cl 2 ) via cannula . the reaction was allowed to proceed for 12 h followed by quenching in water . the organic layer was extracted with diethyl ether ( et 2 o ) and subjected to gc - ms analysis to determine product composition and distribution . the reaction schemes and obtained results are provided in fig2 and 22 . poly ( 3 - hexylthiophene ) ( ht - pht ) was prepared by the original method that provides a high specificity of h - t configuration of the repeating units (& gt ; 98 %) h - t coupling ). the mechanism of the cross - coupling chain growth polymerization is outlined in fig2 . the first step in the mechanism , where the 2 - bromo - 5 - chlorozinc 3 - hexylthiophene monomer ( 1 ) generated in situ from 2 - bromo - 3 - hexylthiophene reacts with ni ( dppp ) cl2 yielding the organonickel compound ( 2 ), is as it has been described by others . here , the difference in the mechanism in that reductive elimination of 2 immediately forms an associated pair ( 3 - 4 ) of the tail - to - tail aryl halide dimer ( 4 ) and nickel ( 0 ) ( 3 ). the dimer 4 undergoes fast oxidative addition to the nickel center generating 5 in view of the fact that the formation of the complex 3 - 4 eliminates potential separation of 4 from 3 . subsequently , growth of the polymer chain occurs by insertion of one monomer at a time as shown in the reaction cycle ( 5 -→ 6 -→[ 3 - 7 ]-→ 5 ) where the ni ( dppp ) moiety is incorporated into polymer chain as end group . addition of various grignard reagents ( rmgx ) at the end of polymerization results in end - capping of ht - pats with r ′ end group , which supports the fact that ni ( dppp ) cl2 acts as an initiator rather than a catalyst . furthermore , adding organometallic ( e . g ., magnesium or zinc ) thiophene bromides to species 5 results in the formation of block copolymers , providing a strong evidence for the living nature of this polymerization . in a typical polymerization experiment , a dry 100 ml three - neck flask was flashed with dinitrogen ( n 2 ) and was charged with diisopropylamine ( 0 . 50 ml , 3 . 5 mmol ) and thf ( 30 ml ); both were added via a syringe . the reaction flask was cooled to 0 ° c ., and n - butyllithium ( 2 . 0 ml , 3 mmol ) was added dropwise via syringe . after 20 min of stirring at 0 ° c ., the solution was chilled to − 76 ° c . ( acetone / dry ice bath ), and stirring continued for 5 min . to this reaction mixture a previously chilled to − 76 ° c . 0 . 3 m solution of 2 - bromo - 3 - hexylthiophene ( 0 . 73 g , 3 mmol ) in anhydrous thf ( 10 ml ) was added via cannula . the reaction mixture was stirred for 1 h at − 76 ° c ., at which time anhydrous zncl 2 ( 0 . 50 g , 3 . 6 mmol ) was added in one portion and completely dissolved after 30 min of stirring . the cooling bath was removed , and the reaction mixture was allowed to warm to rt , at which time 2 , 2 ′- bithiophene ( 0 . 16 g , 1 mmol ) was added in one portion and used as an internal standard . to this mixture ni ( dppp ) cl 2 ( 29 mg , 0 . 053 mmol ) was added in one portion , and the reaction mixture was stirred at rt . aliquots ( 1 ml ) were taken at different time intervals ( e . g ., 1 , 3 , 5 , 8 min etc ., and the final aliquot was taken at 12 h ), and each was precipitated in methanol ( 5 ml ). for each aliquot a gc sample was prepared in et 2 o ( 2 ml ) and was subjected to analytical gc and subjected to gc - ms analysis . after filtration , the molecular weight of the pristine polymer samples was measured by gel permeation chromatography ( gpc ) on a waters 2690 separations module apparatus and a waters 2487 dual λ absorbance detector with chloroform as the eluent ( flow rate 1 . 0 ml / min , 35 ° c ., λ = 254 nm ) with a series of three styragel columns ( 10 4 , 500 , 100 å ; polymer standard services ). toluene was used as an internal standard , and calibration based on polystyrene standards was applied for determination of molecular weights . gc - ms was performed on an agilent 6890 - 5973 gc - ms workstation . the gc column was a hewlett - packard fused silica capillary column cross - linked with 5 % phenylmethyl siloxane . helium was the carrier gas ( 1 ml / min ). unless otherwise noted , the following conditions were used for all gc - ms analyses : injector temperature , 250 ° c . ; initial temperature , 70 ° c . ; temperature ramp , 10 ° c ./ min ; final temperature , 300 ° c . to support the proposed chain growth mechanism , several experiments were performed at constant monomer concentration and variable ni ( dppp ) cl 2 concentration . all the reactions were very fast , reaching almost 90 % conversion in less than 2 h at room temperature . the reaction rates increased with the increase in ni ( dppp ) cl 2 concentration ( fig2 ). linear semilogarithmic kinetic plots were obtained up to 50 % conversion ( e . g ., [ m ] 0 :[ ni ( dppp ) cl 2 ]= 49 : 1 ). the nonlinearity of semilogarithmic kinetic plots would , however , indicate the presence of termination reactions , which could be due to the formation of large supramolecular aggregates of polymer species mixed with unassociated or very weakly associated polythiophene chains . a reaction order of about 1 with respect to ni ( dppp ) cl 2 concentration was obtained from the slope of the plot of the logarithm of the initial rate of polymerization vs the logarithm of the ni ( dppp ) cl 2 concentration . the molecular weight vs . conversion plot ( fig2 ) and the gpc traces ( fig2 ) show the increase of molecular weight with conversion , providing a further support for the mechanism of the nickel - initiated cross - coupling polymerization being a chain process . the results indicate that the molecular weight of polymer can be predicted by the molar ratio of monomer to ni ( dppp ) cl2 which means that 1 mol of ni ( dppp ) cl2 initiates one polymer chain . in previous work , relatively low concentrations of ni ( dppp ) cl2 was used which leads to higher molecular weights and broad pdis as illustrated in fig2 ( e . g ., [ m ] 0 :[ ni ( dppp ) cl2 ]= 136 : 1 ; mw / mn ranges from 1 . 2 to 1 . 6 ). when a lower ratio of monomer to initiator is employed , however , one finds a good correlation between the theoretical and observed molecular weights , and narrow pdis are obtained ( e . g ., [ m ] 0 :[ ni ( dppp ) cl2 ]= 49 : 1 ; mw / mn ranges from about 1 . 2 to 1 . 3 ). fig2 shows the plot of the logarithm of the initial rate of polymerization vs . the logarithm of the ni ( dppp ) cl 2 concentration for temperature of 23 - 25 ° c . ; [ m ] 0 = 0 . 075 mol / l . the present description also refers to the following references which are incorporated by reference in their entirety . while these references may be referred to in the practice of the present invention , no admission is made that any of these references are prior art . 1 . skotheim , t ., handbook of conducting polymers . ed . ; marcel dekker : new york , 1986 . 2 . skotheim , t . ; reynolds , j . ; elsembauer , r ., handbook of conducting polymers . ed . ; marcel dekker : new york , 1998 . 3 . nalwa , h . s ., handbook of organic conductive molecules and polymers . ed . ; 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