Final Copolymer Research Articles

Nanoparticles carrying hydroxyl groups produced by microemulsion

AbstractMethylmethacrylate and 2‐hydroxyethylmethacrylate were polymerized in oil‐in‐water microemulsions that were stabilized by cetyltrimetylammonium bromide (CTAB). Microemulsions that prepared changed continuously from transparent microemulsions to turbid emulsions by increasing the HEMA weight percentage as a comonomer. Polymerization was initiated with an oil‐soluble initiator, azobisizobutyronitrile (AIBN). Stable P(MMA‐HEMA) latexes were obtained about 40 nm in diameter. Molecular weights of the copolymers were in the range of 1.89–2.03 × 106. The glass transition temperatures of these copolymers, which were obtained by differential scanning calorimeter, were in the range of 95–99°C. The comonomer ratio in the final copolymers were obtained from the nuclear magnetic resonance spectra, which were smaller than the comonomer ratios used in the original recipes. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 237–242, 2001

The Synthesis of Liquid Crystalline Copolymers with Block Copolymer Grafts

The synthesis of novel copolymers consisting of a side-group liquid crystalline backbone and poly(tetrahydrofuran)-poly(methyl methacrylate) block copolymer grafts was realized by using cationic-to-free-radical transformation reactions. Firstly, photoactive poly(tetrahydrofuran) macroinimers were prepared by cationic polymerization of tetrahydrofuran and subsequent termination with 2-picoline N-oxide. Secondly, the macroinimers and acrylate monomers containing different spaced cyanobiphenyl mesogenic groups were copolymerized to yiel the respective graft copolymers. Eventually, these were used for indirect photochmical polymerization of methyl methacrylate by UV irradiation in the presence of anthracene as a photosensitizer leading ti the final copolymers with block copolymer grafts. The liquid crystalline, semi-crystalline, and amorphous blocks were micro-phase separated in the graft copolymers.

Optimal carbon source switching strategy for the production of PHA copolymers

AbstractDuring polymerization in a nongrowing cell population of Ralstonia eutropha, alternating between two different carbon sources (fructose and fructose/valeric acid) could lead to the production of block copolymers consisting of blocks of homo‐poly‐3‐hydroxybutyrate (PHB) and polyhydroxybutyrate‐co‐valerate (PHBV) copolymer. The problem of finding the optimal number of carbon source switches and corresponding switching times that maximize the final concentration of diblock copolymers (PHB‐PHBV and PHBV‐PHB) was addressed. It was mathematically formulated in the mixed‐integer nonlinear programming (MINLP) framework, which allows the decomposition of the original problem into the primal and master problems. The primal problem corresponds to the original problem for a fixed number of carbon source switches, whereas the master problem consists of finding the number of carbon source switches that maximizes the optimum solutions of all possible primal problems. The global optimum was obtained for 39 carbon source switches. It corresponds to a mass fraction of 50.6% of final diblock copolymer concentration over the final total polymer concentration.

Increased Reactor Performance versus Reactor Safety Aspects in Acrylate Copolymerization

The aim of reducing cycle times of semibatch-polymerization processes requires systematic investigations of the kinetics, careful adjustment of the desired polymer properties, proper thermal reactor design and reliable reactor safety assessment [1]. As a concrete example, a semibatch-copolymerization was carefully examined with respect to four different aspects. Thermo-kinetics of the reaction were investigated with isoperibolic reaction calorimetry and GC. In order to obtain reliable values for the overall heat transfer coefficient of the production scale reactor, cooling experiments were carried out with solvent and final copolymer solution as reactor content. For consistent reactor safety assessment additional investigations are necessary including case studies of breakdown incidences. These simulations were performed with a mathematical model based on the GC data and experimental vapor pressure curves. As a result of these calculations, a reduction of reaction time from 10 to 6 hours was possible. To convert into practice, it must be ensured that even in this shortened time a product of the same quality is produced.

Semiconducting Diblock Copolymers Synthesized by Means of Controlled Radical Polymerization Techniques

A donor−acceptor, rod−coil diblock copolymer has been synthesized with the objective of enhancing the photovoltaic efficiency of the PPV−C60 (PPV = poly(p-phenylenevinylene)) system by the incorporation of both components in a molecular architecture that is self-structuring through microphase separation. Diblock copolymers were obtained by using an end-functionalized rigid-rod block of poly(2,5-dioctyloxy-1,4-phenylenevinylene) as a macroinitiator for the nitroxide-mediated controlled radical polymerization of a flexible poly(styrene-stat-chloromethylstyrene) block. The latter block was subsequently functionalized with C60 through atom-transfer radical addition. In a spin-cast film of the final diblock copolymer, the luminescence from PPV is strongly quenched, indicating efficient electron transfer to C60. Under suitable conditions, solution-cast films of these diblock copolymers exhibit micrometer-scale, honeycomb-like patterns of holes.

Synthesis and aqueous solution properties of novel neutral/acidic block copolymers

The synthesis of novel acidic diblock copolymers via group transfer polymerisation (GTP) is described. Oligo(ethylene glycol) monomethyl ether monomethacrylate (OEGMA) was copolymerised with either benzyl methacrylate (BzMA) or tetrahydropyranyl methacrylate (THPMA). The BzMA and THPMA act as protected monomers for the methacrylic acid residues, which cannot be polymerised directly using GTP. Provided that the BzMA content of the copolymer is not too high, the benzyl groups can be selectively deprotected by catalytic hydrogenolysis to give the corresponding methacrylic acid copolymers. However, incomplete debenzylation of BzMA-rich copolymers and contamination of the final deprotected copolymers with catalyst residues limited the utility of this synthetic route. On the other hand, THPMA-based copolymers could be deprotected by acidic hydrolysis under mild conditions to give well-defined OEGMA–MAA copolymers. In this case quantitative deprotection was achieved regardless of the block composition and no catalyst contamination problems were encountered. In addition, aqueous GPC confirmed that the narrow molecular weight distributions of the precursor blocks were retained in the final OEGMA–MAA copolymers. Hence, although THPMA is not commercially available, it is preferred to BzMA for the convenient synthesis of OEGMA–MAA block copolymers. Finally, reversible micellisation of selected OEGMA–MAA block copolymers was observed in aqueous media. In the presence of 1M K2CO3 the OEGMA chains form the micelle cores, whereas the neutral MAA block forms the micelle core at pH 1. In both cases NMR studies suggest that the micelle cores remain highly hydrated.

Methacrylate-based nanoparticles produced by microemulsion polymerization

Nanoparticles of methacrylate comonomers were obtained by microemulsion polymerization by using cetyltrimethylammonium bromide as the stabilizer. Stable and bluish transparent latexes were produced from these polymerizations in which potassium persulphate was used as the initiator. The viscosity average molecular weights were in between 6 × 105 and 1.25 × 106. The average diameters of the latex particles were in the range of 20–40 nm, which was obtained by scanning tunneling microscopy. The average particle diameter increased both with an increase in the relative amount of the comonomers and their type. The glass transition temperatures of these polymers obtained by DSC were in the range of 30–103°C, and decreased with the increase in the comonomer ratio. The comonomer ratios in the final copolymers were obtained from 1H-NMR spectra, which were smaller than those ratios used in the original recipes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 569–575, 2000

Lower critical solution temperatures of N-substituted acrylamide copolymers in aqueous solutions

Several series of copolymers were prepared from N-substituted acrylamides by free radical polymerization in solution. We have selected a group of monomers with varying degree of hydrophilicity including acrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, and N-tert-butylacrylamide. The chemical composition in the final copolymers was found to be very close to the original monomer composition in the feed prior to polymerization. In an effort to elucidate the effect of the chemical composition on the phase separations of the aqueous solutions of the copolymers, the lower critical solution temperatures (LCST) of the copolymers in water were determined by differential scanning calorimetry and optical turbidimetry. In principal, the LCST of the copolymers can be adjusted within the freezing and boiling points of the solutions. The copolymers exhibit systematic changes in their LCSTs as a function of their comonomer composition, for which an empirical equation was established.

Selective properties of polyester and cotton/polyester fabrics gamma radiation grafted with different binary mixtures of vinyl monomers

Radiation graft copolymerization of individual and comonomer mixtures of vinyl monomers onto polyester and cotton/polyester fabrics by the mutual method has been investigated. The effect of factors that may affect the grafting yield, such as solvent composition, comonomer mixture composition and radiation dose, have been examined. Suitable conditions that gives the highest graft yield without altering the original properties of the substrates are reported briefly. An attempt was made to determine the graft yield fraction from each monomer in the final graft copolymer in the case of grafting comonomer mixtures by using elemental analysis of nitrogen. Moreover, the results of elemental analysis were used to determine the reactivity ratios of the vinyl monomers. Some selective properties of the graft copolymers of polyester and cotton/polyester with the individual and comonomer mixtures have been investigated. The studied properties are the dye affinity for various dyestuffs and the mechanical properties in terms of tensile strength, elongation at break and Young's modulus. In general and regardless of the system used, grafting improves the dyeability of polyester and cotton/polyester with basic, vat, acid and disperse dyes. Also, it was found that improvement in dyeing and mechanical properties depends essentially on the composition of the graft copolymer and not on the composition of the feed comonomer solution or the total graft yield. © 1999 Society of Chemical Industry

Synthesis of water-soluble statistical copolymers and terpolymers containing pendent oligo(ethylene glycol derivatives)

A series of water-soluble pendent oligo(ethylene glycol)-based statistical copolymers and terpolymers were synthesised using group transfer polymerisation (GTP). More specifically, oligo(ethylene glycol) monomethyl ether monomethacrylate (OEGMA) macromonomers containing 6, 21 or 44 ethylene glycol units were copolymerised with either benzyl methacrylate (BzMA), 2-(dimethylamino)ethyl methacrylate (DMAEMA) or tetrahydropyranyl methacrylate (THPMA) to give statistical copolymers. The analogous terpolymers were obtained by copolymerising the oligo(ethylene glycol) monomethyl ether monomethacrylates with n-butyl methacrylate (nBuMA) and either BzMA or DMAEMA. Gel permeation chromatography was used to determine copolymer molecular weights and polydispersities, while proton NMR spectroscopy was used to assess their compositions. In all cases, the final copolymers were near-monodisperse (Mw/Mn’s < 1.2) and good molecular weight control was achieved. The BzMA-containing copolymers were deprotected via catalytic hydrogenolysis to selectively remove the benzyl groups, giving polymers containing carboxylic acid groups. Similarly, the THPMA-containing polymers were deprotected by acidic hydrolysis to remove the tetrahydropyranyl groups, also resulting in acidic statistical polymers. Comparison of the degrees of deprotection achieved using the BzMA and THPMA protected monomers suggests that THP is the preferred protecting group since it is removed quantitatively regardless of the copolymer composition. In contrast, incomplete deprotection was obtained for the copolymers containing more than 67mol% BzMA.

Synthesis of novel block and statistical methacrylate-based ionomers containing acidic, basic or betaine residues

Group-transfer polymerisation (GTP) has been used to synthesise a range of statistical and block methacrylate copolymers containing a small fraction (10–30 mol%) of ionic residues. More specifically, n-butyl methacrylate (nBuMA) and benzyl methacrylate (BzMA) were copolymerised using GTP. The precursor copolymers were then deprotected via catalytic hydrogenolysis to selectively remove the benzyl groups, giving a range of statistical and block copolymers containing carboxylic acid groups. Similarly, copolymerisation of nBuMA with 2-(dimethylamino)ethyl methacrylate (DMAEMA) directly yielded copolymers containing tertiary amine groups. Zwitterionic and cationic derivatives of these copolymers were obtained by betainisation and quaternisation of the DMAEMA residues, respectively. Gel permeation chromatography was used to determine copolymer molecular weights and polydispersities, while proton n.m.r. spectroscopy was used to assess their composition. In all cases, the final copolymers were near-monodisperse (Mw/Mn < 1.15) and good molecular weight control was achieved.

Application of diol dimethacrylates in dental composites and their influence on polymerization shrinkage

Diol dimethacrylates (DD) that possess long aliphatic chains were incorporated into the conventional dental resin mixtures (e.g., BIS-GMA and TEGDMA) in order to reduce the polymerization stress and shrinkage of final copolymers. It was found that the polymerization shrinkage of the standard copolymer (60 mol % BIS-GMA and 40 mol % TEGDMA) could be reduced even by 20% when TEGDMA is substituted by a long aliphatic diol dimethacrylate. These phenomena can be attributed to the low miscibility of BIS-GMA and DD, which causes long aliphatic chains of DD to remain in coil form in a reaction mixture. The coils can be unwound and expand as a result of the formation of covalent bonds during polymerization and thus reduce the polymerization shrinkage. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2333–2337, 1997

Epoxy-based divinyl ester resin/styrene copolymers: Composition dependence of the mechanical and thermal properties

Epoxy-based divinyl ester resins (DVER) were obtained by reacting diglycidyl ether of bisphenol A (DGEBA) with methacrylic acid (MA) and characterized by FTIR and 1H-NMR spectroscopies and gel permeation chromatography (GPC). The densities and viscosities of the DVER in styrene (S) solutions were measured at different temperatures, 25, 40, and 60°C and compositions, 3.4 to 100% by weight of styrene. Dynamic mechanical measurements (DMA) and differential scanning calorimetry (DSC) were used to determine the glass transition temperatures of the homopolymers and the DVER/S copolymers: 20, 40, 60, and 80% by weight of styrene. The values obtained are in the range limited by the homopolymers glass transition, 100°C for polystyrene and 173°C for the cured DVER. The data were well fitted if two contributions to the glass transition are taken into account: the “linear copolymer” contribution (Fox eq.) and the “crosslinking” contribution (Nielsen model). Uniaxial static compression tests were carried out to determine the modulus, yield stress, and ultimate stress in samples with different compositions. All the mentioned properties decrease with an increase in the styrene concentration in the final copolymer. It was found that the volumetric contraction during curing increases with styrene concentration. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1059–1066, 1997

Functionalization of Poly(organophosphazenes). 8. Thermally-Induced Grafting Reactions of Maleates onto Poly[bis(4-ethylphenoxy)phosphazene

In this paper the radical-induced solution grafting of diethyl maleate onto poly[bis(4-ethylphenoxy)phosphazene] is reported, together with the possible parameters that can influence this reaction, i.e., the maleate, molecular oxygen, and dicumylperoxide concentration in the reaction mixture, the solvent, time, and temperature of the process. A possible mechanism of this process is inferred on the basis of literature data concerning analogous grafting processes carried out onto polyolefins. The importance of the decrease of the intrinsic viscosity of the reaction mixture that takes place during the grafting reaction is also discussed in terms of chain scission and molecular weight degradation of the phosphazene macromolecule. The possible implication of the final phosphazene copolymers containing variable quantities of grafted diethyl succinate groups, poly[bis(4-ethylphenoxy)phosphazene]-g-diethyl succinate, in blending processes with commercial, carbon-backboned macromolecules (polyesters and polycarbon...

Ligated anionic block copolymerization of methyl methacrylate withn-butyl acrylate andn-nonyl acrylate as promoted by lithium 2-(2-methoxyethoxy) ethoxide/diphenylmethyllithium

Poly(methyl methacrylate-b-n-butyl acrylate) (PMMA-b-Pn-BuA) and poly(methyl methacrylate-b-n-nonyl acrylate) (PMMA-b-Pn-NonA) diblock copolymers have been successfully synthesized by the sequential anionic polymerization of methyl methacrylate (MMA) and the n-alkyl acrylate (n-BuA or n-NonA), in a 90/10 toluene/tetrahydrofuran (THF) mixture at −78°C. When diphenylmethyllithium (DPMLi) ligated with lithium 2-(2-methoxyethoxy) ethoxide (LiOEEM) is used as the initiator, the polymerization of each block appears to be living. Molecular weight and composition of block copolymers can be predicted from the monomer over initator molar ratio and the molecular weight distribution is narrow. Size exclusion chromatography (SEC) supports that no homo-PMMA contaminates the final copolymer. Although the reverse polymerization sequence Pn-NonA-b-PMMA always results in some contamination by homo-Pn-NonA, it has no really significant effect on the final product characteristics. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1543–1548, 1997

Water soluble polymers: 69. pH and electrolyte responsive copolymers of acrylamide and the zwitterionic monomer 4-(2-acrylamido-2-methylpropyldimethylammonio) butanoate: synthesis and solution behaviour

A novel carboxybetaine monomer, 4-(2-acrylamido-2-methylpropyldimethylammonio) butanoate (AMPDAB), has been synthesized and copolymerized with acrylamide in an aqueous NaBr solution. The feed ratio of AM ( M 1)/AMPDAB( M 2) was varied from 90 10 to 0 100 mol% . Low conversion samples were collected and copolymer compositions were determined with 13C n.m.r. by integration of the carbonyl resonances. Reactivity ratios were determined and the nonlinear least-squares method yielded values of r 1 = 1.01 and r 2 = 0.99, indicating random incorporation of monomers into the final copolymer. Molecular weights were determined and range from 3.9 to 12.0 × 10 6 g mol −1. The solution behaviour of the above copolymers was studied as a function of pH and added electrolytes. With the exception of the copolymers containing 60 and 75 mol% AMPDAB, homogeneous solutions were obtained in deionized water. At high pH, the polyzwitterions show an enhancement in viscosity as the concentration of added electrolyte is increased. In deionized water, as the pH of the aqueous media is lowered, the copolymers exhibit a dramatic increase in viscosity as the carboxylate groups are protonated and charge-charge repulsions of the quaternary ammonium groups induce polyelectrolyte behaviour. The solution behaviour is compared to structurally similar sulfobetaines which do not exhibit any responsiveness to changes in pH.

Thermal treatment of poly[ethylene‐alt‐2,2‐bis(1,4‐phenylene)propane carbonate]: A reinvestigation

AbstractThe final product of the thermal treatment of poly[ethylene‐alt‐2,2‐bis(1,4‐phenylene)‐propane carbonate] (polymer 1) at 280°C under vacuum was characterized as a random copolymer containing both ether and carbonate groups and not as pure bisphenol A polycarbonate as reported previously by other authors. Infrared and NMR spectroscopy were used to detect the changes of the polymer structure during the thermal treatment; the resulting polymers were also characterized by measuring their intrinsic viscosity. During the thermal treatment different reactions occur: exchange reactions (which would lead to a random copolycarbonate), and intramolecular elimination of ethylene carbonate and carbon dioxide. This last elimination is responsible for the formation of ether groups which, being stable under the reactions conditions, prevent the complete elimination of the aliphatic moieties. The final random copolymer was also prepared by reacting pure bisphenol A polycarbonate (PC) and ethylene carbonate; this confirms the occurrence of exchange reactions, which lead to a random copolycarbonate having a structure similar to the polymer deriving from polymer 1. Surprisingly, in the presence of a typical exchange reaction catalyst such as dibutyltin dimethoxide or titanium tetrabutoxide, the final product of the thermal treatment of polymer 1 is pure PC.

Water-soluble polymers. 72. synthesis and solution behavior of responsive copolymers of acrylamide and the zwitterionic monomer 6-(2-acrylamido-2-methylpropyldimethylammonio) hexanoate

A novel carboxybetaine monomer, 6-(2-Acrylamido-2-methylpropyldimethylammonio) hexanoate (AMPDAH), has been synthesized and copolymerized with acrylamide in an aqueous NaBr solution. The feed ratio of AM (M1): AMPDAB(M2), was varied from 98.5 : 2.5 to 0 : 100 mol %. The polymerizations were carried out to 20–30% conversion. Copolymer compositions were determined with 13C NMR by integration of the amido carbonyl resonances. Reactivity ratios determined from the nonlinear least-squares method gave values of r1 = 0.98 and r2 = 0.85, indicating random incorporation of the comonomers into the final copolymer. Molecular weights ranged from 7.3 to 4.7 × 106 g/mol. The solubility behavior of the copolymers is dependent on the mol % AMPDAH incorporated into the copolymers. When 25 mol % or more is incorporated, the copolymers are only swellable in aqueous media and attempts to solubilize these systems were unsuccessful. AMPDAH incorporation of 10 mol % or less resulted in copolymers soluble in aqueous media under a variety of conditions. The viscometric properties of copolymers with 10 mol % or less is reported as a function of pH and added electrolytes. At high pH in deionized water, the polyzwitterions show both inter- and intramolecular associations, which are disrupted by the addition of sodium chloride. In deionized water, as the pH of the aqueous medium is lowered, the copolymers exhibit dramatic increases in viscosity as the carboxylate groups are protonated and charge–charge repulsions of the quaternary ammonium groups induce polyelectrolyte behavior. © 1997 John Wiley & Sons, Inc.

Synthèse de l'acide 2‐acrylamido 2‐méthylpropanoïque et copolymérisation avec l'acrylamide

AbstractThe synthesis of 2‐acrylamido‐2‐methylpropanoic acid (2A2MPA) was carried out starting from 2‐methylpropanoic acid. Copolymerizations of the 2A2MPA salt (2A2MPANa, monomer A) with acrylamide (AM, monomer B) were investigated using K2S2O8 as initiator. They were terminated before reaching 15% conversion. A range of feed compositions was selected (2A2MPANa increasing from 10 to 100 mol‐%) and the compositions of the copolymers obtained were assessed through 13C NMR. The reactivity ratios for the couple A, B were determined as rA = 0,76 and rB = 1,06. One additional copolymerization was allowed to reach 100% conversion, and the final copolymer showed interesting drag reduction properties.

A new method for fabricating high performance polymeric thin films by chemical vapor polymerization

A vacuum deposition method is presented in which copolymer films are grown from a vinylic monomer chosen for desirable properties and paraxylylene. The concentration of paraxylylene in the final copolymer can be negligibly small if proper deposition conditions, presented here for the first time, are employed. Films of paraxylylene with N-phenyl maleimide deposited at 40 °C, for example, showed thermal stability and FTIR spectra nearly identical with homopolymers of poly(N-phenyl maleimide). Different rate-limiting steps are proposed to explain film composition; paraxylylene is under surface reaction control, while the comonomer obeys mass flow control. This results in a deposition environment extremely rich in comonomer. Growth rates and compositions were consistent with predictions. The initiation reaction did not appear different from homopolymerization of paraxylylene. The general method presented here allows fabrication of vapor-deposited thin films with properties limited primarily by the comonomer employed.