bluuebunny/crossref_metadata_2025_split huggingface dataset:
Copolymer composition control during the seeded emulsion copolymerization of vinyl acetate and methyl acrylate
Authors: Arzamendi Gurutze , Asua José M. 
Published: March 2011

AbstractThe effect of various monomer addition policies on the copolymer composition during the seeded copolymerization of methyl acrylate and vinyl acetate in a semicontinuous reactor was investigated. Four policies were considered. In the first, which is called optimal policy, the reactor was initially charged with all of the less reactive monomer (vinyl acetate) plus the amount of the more reactive monomer (methyl acrylate) needed to initially form a copolymer of the desired composition. Then, the addition of the remaining methyl acrylate was made at a flow rate that ensured the formation of a copolymer of the desired composition. In the second, the initial charge is the same as in the previous case but the time dependent addition rate of methyl acrylate was decomposed into three periods of constant feed rate. In the third, the initial charge is the same as in the previous policies but the remaining methyl acrylate was added at a constant feed rate. In the forth, both monomers were added under starved conditions. In order to calculate the optimal addition policy, the time evolution of the average number of radicals per particle, ñ, is required. The calculation of ñ involves rate parameters which values are usually unknown. Therefore, a semi‐empirical method for the calculation of the time evolution of ñ was developed. It was found that ñ was always greater than 2. For the experimental conditions used in this work, this result suggested that termination in the polymer particles was affected by gel effect. A gel effect function was estimated and then the optimal addition policy was calculated. Comparison between the different processes showed that, for a fixed process time, the copolymer obtained through the optimal addition policy was more homogeneous than that formed when the methyl acrylate was fed in three periods of constant feed rate and even better than the one obtained using a constant feed rate throughout the process. The copolymer quality of the later process is similar to that of the copolymer formed by means of the starved process. Nevertheless, a more homogeneous copolymer composition can be obtained through the starved process when longer process times are used.
Modelling and simulation of emulsion copolymerization of monomers of different polarities ‐ relationship polymerization process ‐ microstucture ‐ properties
Authors: Guillot Jean 
Published: March 2011

AbstractAccurate kinetic investigations of emulsion copolymerization of monomers of different polarity have allowed to derive reliable mechanisms which appeared to be more complex than usually expected: polymerization in the water phase seems quite general; the solid content ‐ i.e. monomer/water ratio ‐ or, even the pH(when copolymerizing ionogenic monomers) modify the reactivity ratios in emulsion copolymerization; monomer partition is an upmost parameter. However, it is believed that what may be the monomers and the polymerization process, it is possible to model emulsion copolymerization and to develop simulation softwares. These computer simulations then allow to quantitatively compare theoretical behaviour with experimental data and to improve our knowledge of emulsion process. Furthermore, these programs give the sequence distribution of emulsion copolymers and can predict some important properties like the glass transition, which is closely related to copolymer microstructure and hetero‐geneity. Modelling and simulation have been applied to a lot of emulsion copolymerizations and terpolymerizations of various monomers, including some functional monomers.
Recent developments in the functionalization of latex particles
Authors: Pichot C. 
Published: March 2011

AbstractA survey of the recent literature is given concerning the synthesis and characterization of functionalized latex particles. Two main methods have been particularly considered and discussed: first, the functionalization of latexes by copolymerization of a basic monomer with adding small amount of a monomer bearing a chemical reactive group, with a special emphasis on the kinetics, the distribution of the functional monomer, the surface morphology of latex particles and the optimization of processes; secondly, the use of surface‐active monomers in such reactions which may confer potential advantages (low level of water‐soluble polymers, control of surface charge density) in comparison with the former ones, provided further information can be obtained on their kinetic behavior in emulsion polymerization.
Synthesis of reactive latices by copolymerization of methyl acrylamidoglycolate methyl ether (MAGME) with styrene and butyl acrylate
Authors: Magnet S. , Guillot J. 
Published: March 2011

AbstractA reactive latex Styrene (S) ‐ Butyl Acrylate (BuA) functionalized with methyl acrylamidoglycolate methyl ether (MAGME) has been synthesized in emulsion and characterized, which can be further crosslinked with other adapted reactive latices. This work deals mainly with kinetics and location of the monomers and with a comparison between experimental and simulated data based on monomer partition and reactivities. The three stages polymerization of hydrophilic MAGME has been quantitatively explained. From the change in overall propagation rate constants and DSC thermograms, it is concluded that particles are structured with a core richer in S and a shell richer in BuA, a huge amount of MAGME being polymerized in the water phase as hydrosoluble polymer strongly adsorbed onto particles and forming a reactive ultimate layer.
Polymer physics and characterization by mechanical measurements
Authors: Cavaillé J. Y. , Perez J. 
Published: March 2011

AbstractThe characterization and the study of the physical properties of polymeric materials need the use of many different experimental techniques. Among them, the mechanical behavior can be considered as a probe able to characterize the molecular mobility if suitable theoretical approaches can relate the macroscopic behavior to microscopic events. Many works have been done using two different types of tests: (i) tests involving stress large enough to induce non‐linear behavior (plastic flow…), (ii) mechanical spectrometry technique or microcreep which involve stress lower than 105 Pa. An attempt have been done to give a unitary description of the behaviors observed under these two conditions. The case of multiphase polymer materials is obviously more difficult, but because the mechanical properties are mainly sensitive on one hand to the behavior of each phase and on the other hand to their geometrical and topological arrangements, it is possible, from mechanical tests, to obtain information about these both aspects.
Influence of chemical heterogeneity on structure and properties of emulsion copolymers
Authors: Zosel A. , Heckmann W. , Ley G. , Mächtle W. 
Published: March 2011

AbstractWhen comonomers of different hydrophilicity are copolymerized in emulsion polymerization, a heterogeneous distribution of the polar groups in the resulting latex can occur which is mainly caused by differences in the solubilities of the monomers as well as the polymerization products in the water and the polymer phase. By a combination of various methods, analytical ultracentrifugation of the latices, mechanical spectroscopy, tensile tests and electron microscopy of the latex films, the distribution of the polar groups in the latex, the structure of the latex particles, and the morphology and mechanical behaviour of the latex films have been studied. Films of emulsion copolymers in many cases show a very pronounced two‐phase morphology consisting of the main polymer within the particles and a second hard phase which is concentrated in the interfaces and wedges between the original particles, forming a honeycomb‐like continuous structure throughout the film which has a strong influence on the mechanical properties of the films. When emulsion copolymers are cross‐linked via reactive monomers with a higher degree of hydrophilicity than the main monomers, structurized networks may result with a spatially inhomogeneous distribution of cross‐links. Structure and properties of films from emulsion copolymers are determined by the polymer bulk properties as well as the multiphase structure.
Characterisation of partially‐hydrolysed poly(vinyl acetate)s for use as stabilisers in suspension polymerisation
Authors: Goodall A R , Greenhill‐Hooper M J 
Published: March 2011

AbstractThe surface chemical properties of two partially hydrolysed (98% and 88%) poly(vinyl acetate)s derived from the same parent polymer have been correlated with their ability to stabilise styrene and polystyrene suspensions. The 88% hydrolysed polymer adsorbed more strongly at both the monomer/solution and polymer/solution interfaces to give a thicker adsorbed layer, it also had less tendency to desorb at elevated temperatures. Stability studies showed that both styrene emulsions and polystyrene latex particles were more stable in the presence of the 88% hydrolysed polymer. The results illustrate the importance of the degree of hydrolysis on the stabilising power of these polymers.
Novel aqueous dispersion polymers
Authors: Palluel A.L.L. , Westby M. J. , Bromley C.W.A. , Davies S. P. , Backhouse A. J. 
Published: March 2011

AbstractThree novel processes for the synthesis of aqueous dispersions of acrylic polymers are described. In each case, stabilisation of the latex is attributed to the presence of water‐soluble polymer chains grafted to the surface of the polymer particles. Acrylic latices comprising grafted, non‐ionic poly(ethylene glycol) (PEG) stabiliser show excellent stability in surface coating applications and superior resistance properties, in both air dried and thermally cured coatings. Latices stabilised with grafted polyelectrolyte are useful in thermosetting paints for spray application.
Kinetics of (CO)polymerizations at the surface of inorganic submicron particles in emulsion‐like systems
Authors: Caris C.H.M. , Kuijpers R.P.M. , van Herk A. M. , German A. L. 
Published: March 2011

AbstractHydrophilic TiO2 particles were modified with two different titanates and thus made hydrophobic. “Emulsion” polymerizations were carried out in aqueous dispersions of these particles, stabilized with an anionic surfactant. Polymerization kinetics were determined using a densitometer. The effect of several parameters, like surface modification, surfactant and initiator concentration, and stirring speed on polymerizations were studied. Depending on reaction conditions two competitive polymerizations can take place: one in which polymer is formed at the particle surface and one in which free polymer particles are formed. The TiO2 was modified with a titanate containing a methacrylic acid ester, which was used as a comonomer. Thus a chemical bond between TiO2 particles and polymer was obtained. These polymer encapsulated inorganic particles may offer interesting perspectives in those cases, where a good coupling between particles and matrix is important, for instance in latex paints and in polymer composites.
Tutorial: Thermodynamics of ring‐opening polymerization; Am. Chem. Soc. 199th national meeting, Boston, april 22–27, 1990, 6th international symposium on ring‐opening and cyclo‐polymerization
Authors: Ivin Kenneth J. 
Published: March 2011

AbstractThe ring‐opening polymerization of cyclic monomers shows the characteristic features of any addition polymerization or any physical aggregation process, in particular a ceiling temperature above which the formation of the aggregate (long‐chain polymer), under given conditions of monomer concentration, solvent and pressure, would involve a positive change of free energy and is therefore impossible. Conversely for a given temperature, pressure and solvent, there is an equilibrium monomer concentration below which long‐chain polymer cannot be formed. Cyclic monomers must therefore have a negative free energy of polymerization, under given conditions, if they are to be capable of undergoing a significant extent of ring‐opening polymerization. The effect of monomer structure, including ring size, on thermodynamic polymerizability is discussed, as well as the possibility of copolymerizing monomers which cannot themselves give homopolymers. Examples are given for various possible mechanisms of polymerization.
Synthetic importance and industrial applications of ring‐opening polymerization
Authors: McGrath James E. 
Published: March 2011

AbstractA survey is provided which demonstrates the synthetic importance and variety of industrial applications that have developed for ring‐opening polymerization. The number of polymers produced this way is quite significant and includes the epoxides such as ethylene and propylene oxide and other cyclic ethers such as trioxane, tetrahydrofuran and the epoxy resins. Other important systems include the polylactams such as polycaprolactam (Nylon 6), the siloxane or silicone materials, polycaprolactone, and cycloolefins such as polynorbornene. Polyoxazolines are newer monomers which can be polymerized via cationic mechanisms to yield either hydrophilic or hydrophobic tertiary polyamides. Thus, the importance of the field is quite well established and continues to grow. Major applications in coatings, fibers, elastomers, adhesives, thermoplastics and thermosets, such as in composite matrix resins, have been developed.
Ring‐opening‐closing alternating copolymerization
Authors: Kobayashi Shiro 
Published: March 2011

AbstractThis paper reports a new copolymerization based on the novel concept, i.e., ring‐opening‐closing alternating copolymerization. The reaction of a cyclic monomer A and a noncyclic monomer B takes place without added initiator or catalyst to give a copolymer of structure having a ring‐opened unit from monomer A and a ring‐closed unit from monomer B in alternating arrangement. As monomer A, five, six and seven‐membered cyclic phosphonites are employed. As monomer B, on the other hand, are used muconic acid and dialdehydes. Combinations of these monomers A and B produced in all cases ring‐opened and closed 1 : 1 alternating copolymers.
Aluminium alkoxides: A family of versatile initiators for the ring‐opening polymerization of lactones and lactides
Authors: Dubois Ph. , Jérǒme R. , Teyssié Ph. 
Published: March 2011

AbstractAluminium alkoxides, such as Al(OiPr)3 or Et3‐pAl(O (CH2)2X)p with 1≤p≤3, are very effective in initiating the polymerization of lactones, e.g.ϵ ‐ca‐prolactone and δ ‐valerolactone, and lactides (D,L‐ or L,L‐ isomers). The ring‐opening polymerization proceeds through a “coordination‐insertion” mechanism that involves the selective rupture of the acyl‐oxygen bond of the monomer and its insertion into an Al‐O bond of the initiator. Polymerization is typically “living” and allows block copolyesters with perfectly controlled molecular weight and composition to be prepared. Aluminium alkoxides carrying functional alkoxy groups (X = ‐Br, ‐CH2‐NEt2, ‐CH2‐CH=CH2, ‐CH2‐OC(O)‐C(Me)=CH2…) provide asymmetric telechelic polyesters (end‐groups being ‐X and ‐OH, respectively) and very interesting polyester macromonomers. Coupling the asymmetric telechelic chains via the hydroxyl end‐group ‐ or better its A1 alkoxide precursor ‐ is a straightforward way to the symmetric telechelic polymer bearing the X functional group.
Anionic and pseudoanionic polymerization of ϵ‐caprolactone
Authors: Duda Andrzej , Penczek Stanislaw 
Published: March 2011

AbstractAnionic polymerization of ϵ‐caprolactone conducted in THF solvent has been compared with polymerizations initiated with aluminium alkoxides. The latter processes have been kinetically analysed as the pseudoionic processes, i. e. with propagation proceeding by insertion. In the pseudoanionic reaction active species are aggregated. The methods of solving kinetic schemes involving aggregation ⇋ deaggregation equilibrium, followed by the chain growth on deaggregated species are described. These kinetic methods have been used to determine the propagation rate constants. The relationships between structures of the growing species and their reactivities have thus been determined.
Preparation of functionalized polycarbonates via ring‐opening polymerization of diverse mixed oligomeric cyclic carbonates
Authors: Brunelle Daniel J. , Shannon Thomas G. 
Published: March 2011

AbstractThe preparation and polymerization of a variety of cyclic oligomeric carbonates containing diverse functionality is described. The preparation of bisphenols containing ether, amide, ester, urethane, etherketone, or ethersulfone functionalities is described. The functionalized bisphenols were converted to dichloroformates via phosgenation, and were subjected to cyclization reactions, forming cyclic oligomeric carbonates containing various functionality. Anionic, ring‐opening polymerization of the cyclic oligomers leads to high molecular weight polymers containing carbonate and other functionality. Depending on the nature of the functionalized bisphenol starting material, the product polymers may be alternating, block, or random copolymers.
Thermal and rheological properties of acrylic copolymers possessing crystallizable polyester side chains
Authors: Scholsky K. M. , Orler E. B. , Bixler K. J. , Stackman R. W. 
Published: March 2011

AbstractRing‐opening of ϵ‐caprolactone onto styrene/acrylic acid copolymers was found to occur readily in the presence of a styrene/acrylic acid copolymer at 220 °C. Gel permeation chromatography and extraction experiments utilizing supercritical CO2 suggest that the caprolactone has grafted onto the polymer backbone as polyester side chains. DSC analysis of the modified polymers indicates that the grafted side chains lower the main chain Tg, and when present at sufficiently high levels, contribute crystallinity to the modified materials. Both the melting point and heat of fusion of the modified materials were found to increase as a function of the amount of caprolactone grafted onto the prepolymer. It is unclear whether the formation of crystallites was the result of reaching a critical side chain length, a concentration effect, or a combination of both. The extent of grafting was also found to have a pronounced effect on the melt rheology and rates of crystallization of these materials presumably due to the increased free volume afforded by the polycaprolactone side chains.
Inhibiting or cocatalytic effect of water and other additives on cationic polymerization of cyclodimethylsiloxanes
Authors: Sigwalt P. , Gobin C. , Nicol P. , Moreau M. , Masure M. 
Published: March 2011

AbstractCyclodimethylsiloxanes such as hexamethylcyclotrisiloxane (D3) and octamethyl‐cyclotetrasiloxane (D4) have quite different reactivities and generally do not give the same types of cyclic products. An examination of analogies and differences between these two monomers is made in the case of initiation by trifluoromethane sulfonic acid, for both the formation of water during the reaction and the effect of water and other additives. The differences in the formation of water are much less than was expected and perhaps not really significant. A second analogy is that for both monomers, the retarding or inhibiting effect of water is much stronger when it is premixed with the acid rather than mixed in situ, this being attributed in this last case to a possible competition between monomer and water for the first reaction with acid. From the variation of the rates when the mole ratio [H2O]/[Acid] increases, it is concluded that for the initiation reaction water is a retarder or inhibitor for both monomers while for propagation it is an inhibitor for D4 but a very effective cocatalyst for D3. After a comparison of the effects of added water, silanol and triflic esters on propagation reaction and cyclics formation for these two monomers, and a discussion of the possible active centres, it is concluded that the mechanism of propagation should be different for D3.
Synthesis of poly(dimethylsiloxane)‐nylon‐6 diblock copolymers
Authors: Veith C. A. , Cohen R. E. 
Published: March 2011

AbstractPoly(dimethylsiloxane)‐polyamide‐6 (PDMS‐PA6) diblock copolymers have been synthesized anionically from ω‐N‐acyllactam‐PDMS macroinitiators using newly developed di(tert‐butoxy)‐lithium aluminium hydride catalysts and bulk ultrasonic mixing of the reactants. These copolymers possess high PA6 block molecular weights and good thermal stability in the melt (ca. 250°C) because they do not contain carbamates. Size exclusion chromatography has revealed that traditional catalysts for the ring‐opening polymerization of ϵ‐caprolactam (CPL) such as alkali metal caprolactamates or LiAlH4, significantly depolymerize the PDMS to cyclics (D3, D4) in CPL at moderate temperatures of 100 ‐ 170°C. New coordinating catalysts, produced by derivatizing LiAlH4, reduced the nucleophilicity of the CPL anion but did not interfere with the activated monomer mechanism. These new catalysts eliminated the depolymerization of PDMS to cyclics during growth of the polyamide‐6 block to make the macroinitiator technique viable.
Mechanism of anionic ring‐opening polymerization of silacyclopent‐3‐enes
Authors: Weber William P. , Park Young Tae , Zhou Stephen Q. 
Published: March 2011

AbstractAnionic ring‐opening polymerization of silacyclopent‐3‐enes has characteristics which are different from those of anionic living polymerizations of 1,3‐dienes. High molcular weights are obtained in most cases but generally with most probable molecular weight distributions Mw/Mn ≅ 2. The polymerization is stereospecific. Poly(1‐sila‐cis‐pent‐3‐enes) are obtained. Ring opening polymerization of 1,1,3‐trimethyl‐1‐sila cyclopent‐3‐ene is found to be regioselective at −78°C to yield a polymer in which cis‐1,4‐isoprene units are joined to dimethylsilylene units almost exclusively in a head to tail orientation. Finally, anionic polymerization of 1‐methyl‐1‐silacyclopent‐3‐ene is found to yield poly(1‐methyl‐1‐sila‐cis‐pent‐3‐ene) of low molecular weight. This permits end group analysis by 1H, 13C and 29Si NMR spectroscopy, signals are observed which are consistent with the presence of 1‐methyl‐1‐silacyclopent‐3‐ene rings. These are probably end groups. A mechanism consistent with the above is discussed.
Block copolymer of 2‐methyl‐2‐oxazoline with silica gel an organic‐inorganic hybrid polymer
Authors: Chujo Yoshiki , Ihara Eiji , Kure Shigeo , Suzuki Keisuke , Saegusa Takeo 
Published: March 2011

AbstractRing‐opening polymerization of 2‐methyl‐2‐oxazoline followed by termination with 3‐aminopropyltriethoxysilane produced poly(N‐acetylethylenimine) (polyoxazoline) (POZO) having a terminal triethoxysilyl group. Triethoxysilyl‐terminated telechelic POZO was also prepared by using bifunctional initiators. These silane coupling POZOs were subjected to reaction with silanol groups at the surface of silica gel to modify its surface hydrophilicity. Triethoxysilyl‐terminated POZOs were also subjected to acid‐catalyzed co‐hydrolysis polymerization with tetraethoxysilane by the so‐called sol‐gel method to produce a novel organic‐inorganic hybrid polymer (block copolymer). The hybrid obtained was a homogeneous, transparent, glassy composite material, which showed more hydrophilicity in comparison with that of silica gel without POZO segments. On the other hand, a hybrid polymer consisting of poly(2‐ethyl‐2‐oxazoline) and silica gel showed amphiphilic properties absorbing both water and organic solvents. Pyrolysis of these hybrids at 600°C produced silica having micro‐pores.