Thermal degradation of copolymers of methyl methacrylate and methyl acrylate. I. Products and general characteristics of the reaction

The technique of thermal volatilization analysis (TVA), applied to methyl methacrylate–methyl acrylate copolymers having molar composition ratios 112/1, 26/1, 7.7/1, and 2/1, has demonstrated that the stabilization of poly(methyl methacrylate) by copolymerized methyl acrylate is due to inhibition of the depolymerization initiated at terminally unsaturated structures, probably by direct blockage by methyl acrylate units. The molecular weight of the copolymers decreases rapidly during degradation, suggesting that a random scission process is involved. The products of degradation consist of the monomers, carbon dioxide, chain fragments larger than monomer, and a permanent gas fraction which is principally hydrogen. Infrared and ultraviolet spectral measurements suggest that the residual polymer, which is colored, incorporates carbon–carbon unsaturation. The complete absence of methanol among the products is surprising in view of its abundance among the products of degradation of poly(methyl acrylate). These observations have been accounted for qualitatively in terms of acceptable polymer behavior.     

Friedel-Crafts acylation reactions in copolymers of methyl methacrylate and styrene and in mixtures of the homopolymers

In the presence of SnCl₄ in 1,2-dichloroethane solution, copolymers of styrene and methyl methacrylate undergo a Friedel-Crafts acylation reaction between the ester groups and the ortho position of adjacent styrene units to form a partial ladder polymer. This has been confirmed by infrared and ultraviolet spectral analysis and by observing the influence of substituted styrenes on the rate of the reaction. A similar reaction can be induced to occur between polystyrene and poly(methyl methacrylate). Thermal analysis measurements demonstrate that the degradation properties of copolymers of styrene and methyl methacrylate are profoundly changed by this treatment.     

Thermal degradation of copolymers of methyl methacrylate and methyl acrylate. II. Chain scission and the mechanism of the reaction

It has been established that one molecule of carbon dioxide is produced for each chain scission during degradation of methyl methacrylate–methyl acrylate copolymers with molar compositions in the ratios 112/1, 26/1, 7.7/1, and 2/1. Thus the relatively simple measurement of the production of carbon dioxide can be used to determine the extent of chain scission. In this way the relationships between chain scission and volatilization, zip length, copolymer composition, and the production of permanent gases have been established. The rate of chain scission is proportional to a power of the methyl acrylate content of the copolymer less than 0.5, from which it has been concluded that a significant proportion of the initial production of radicals and the subsequent attack of these radicals on the polymer chains is at random and not specifically associated with the methyl acrylate units. A mechanism for the overall thermal degradation process in this copolymer system is presented in the light of these observations.     

Photodegradation of poly(methyl methacrylate)

The vacuum photodegradation at 30°C. of poly(methyl methacrylate) and copolymers with acrylaldehyde, methacrylaldehyde, and methyl acrylate has been studied. The polymers were examined in the form of expanded films as produced by a freeze-drying technique. At least one molecule of carbon monoxide is evolved for each chain scission. It is concluded that chain scission in poly(methyl methacrylate) is primarily the result of photoinduced aldehyde groups.     

Grafting copolymerization of vinyl monomers on polyimide macroinitiators by the method of atom transfer radical polymerization

Graft copolymers with the main polyimide chain and side chains of poly(n-butyl acrylate), poly(tert-butyl acrylate), poly(methyl methacrylate), poly(tert-butyl methacrylate), polystyrene, and polystyrene-block-poly(methyl methacrylate) were synthesized by atom transfer radical polymerization on the multicenter polyimide macroinitiators in the presence of the halide complexes of univalent copper with nitrogen-containing ligands. Polymerization of metha-crylates is most efficiently developed on the polyimide macroinitiators. The obtained graft copolymers initiate the secondary polymerization (“post-polymerization”) of methyl methacrylate. The conditions of detachment of side chains of graft polymethacrylates that do not involve the ester groups of their monomeric units were found. The molecular mass characteristics of the graft copolymers and isolated polymers, being the detached side chains of the copolymers, were determined. The detached side chains of different chemical structures have low values of the polydispersity index. The procedure developed was used for the preparation of new graft polyimides with side chains of poly-4-nitro-4′-[N-methylacryloyloxyethyl-N′-ethyl]amino-azobenzene that cause the nonlinear optical properties and with the side chains of poly(N,N-dimethylaminoethyl methacrylate) that cause the thermosensitive properties of the copolymers.     

Reversible addition-fragmentation chain transfer copolymerization of methyl methacrylate and methyl acrylate

Pseudo-living radical copolymerization of methyl methacrylate and methyl acrylate under reversible addition-fragmentation chain transfer in a mass in the presence of reversible chain transfer agents of different nature was implemented. A comparison of physical and mechanical properties of narrowly dispersed copolymers was performed as well as copolymers obtained by uncontrolled radical polymerization.     

Polymerization of complexed monomers. II. Alternating copolymers of indene with methyl acrylate and methyl methacrylate

Indene has been copolymerized with polar monomers in the presence of ethylaluminum sesquichloride. The polymers have molecular weights in the 7,000–10,000 range and soften at temperatures above 150°C. The NMR spectra of the copolymers are discussed with reference to polymer structures and chain conformations. Indene is comparable to cyclopentene in reactivity in copolymerizations with methyl acrylate but is much more reactive than cyclopentene toward methyl methacrylate.     

The thermal degradation of copolymers of methyl methacrylate with methacrylic acid

The degradation has been studied using thermogravimetry and thermal volatilization analysis; product analysis has been carried out by GLC and spectroscopy. The copolymers yield water and methanol below 300°; at higher temperatures, the products also include methyl methacrylate, carbon monoxide, carbon dioxide and methane. Quantitative comparison of the yields of methanol and methyl methacrylate has been made with predicted yields based upon sequence distribution calculations. Methanol is believed to result by two routes (i) intramolecular cyclization of adjacent ester and acid chain units at low temperatures, and (ii) fragmentation of ester units, in competition with depolymerization, at higher temperatures. Methyl methacrylate yields are substantially lower than the MMA content of the copolymer, as a result of these processes; some MMA units also appear in the product fraction volatile at degradation temperatures but not at ambient temperature. The partially-degraded copolymers develop anhydride ring structures in the chain as a result both of dehydration and of methanol production. The mechanisms of the various reactions are discussed.     

Photothermal degradation of copolymers of methyl methacrylate and n-butyl acrylate

The photothermal degradation of copolymers of methyl methacrylate (MMA) and n-butyl acrylate (n-BuA) covering the whole composition range has been studied at 165°.The gaseous products, which are relatively minor, are hydrogen, carbon monoxide and methane. The liquid products are predominantly MMA, with n-BuA, n-butanol and n-butyraldehyde as minor products. Infra-red spectral changes in the residue were attributed to lactone formation and associated with butanol formation as in the purely thermal reaction The “cold ring” or chain fragment fraction becomes increasingly more abundant as the n-BuA content of the copolymer is increased.All the products and principal features of the reaction are explained in terms of a radical process which is initiated by scission of pendant acrylate units and is propagated by a combination of depropagation and intra- and intermolecular transfer processes, the relative importance of which depends upon copolymer composition. Differences from the thermal reaction and the corresponding reaction in copolymers of methyl methacrylate and methyl acrylate are discussed.     

Styrene-methyl acrylate copolymers and acrylate homopolymers in solution

Molecular weight determinations by light scattering and osmometry and intrinsic viscosity measurements were made in various solvents on fractions of styrene–methyl acrylate copolymers with different compositions and on acrylate homopolymers prepared by free-radical reaction. Relations between intrinsic viscosity [η] and molecular weight M thus established are compared with those reported by other authors. 2-Methylcyclohexanol was found to be a theta solvent for the copolymers and both parent homopolymers, and isoamyl acetate was a theta solvent for poly(methyl acrylate). From theta point viscosity data obtained with these solvents, unperturbed chain dimensions were estimated. The results are compared with the unperturbed dimensions estimated from the [η]–M relations obtained in good solvents. On the basis of the experimental data it was found that the unperturbed dimension depends linearly on the copolymer composition, in contrast to the case of styrene–methyl methacrylate copolymers. Composition dependences of the theta temperature and of the parameter describing the long-range interactions between nonadjacent segments in polymer chains were investigated. The result implies that long-range interactions between monomeric units never disappear even when those between the same monomeric units vanish. The Huggins constant for copolymer is discussed in terms of the excluded volume variable.     

Photodegradation of copolymers of methyl methacrylate and methyl acrylate at elevated temperatures

Four methyl methacrylate—methyl acrylate copolymers with molar ratios, MMA/MA, of 112/1, 26/1, 7·7/1, and 2/1 have been photodegraded at 170°C by 2537 Å radiation. The changes which occur in the molecular weight of the copolymers are typical of a random scission process and from these and volatilization data the extent of chain scission during the course of the reaction has been calculated. The pattern of volatile products is the same as that previously obtained in the thermal reaction at 300°C although there are a number of differences in detail. For example, only one in ten of the methyl acrylate units is liberated as monomer compared with one in four in the thermal reaction and the ratio CO₂/chain scissions is considerably greater than the strict 1/1 ratio observed in the thermal reaction. Zip lengths are also very much greater in the photo reaction. These minor differences between the two reactions have been accounted for in terms of the mechanism previously presented to account for the thermal reaction, bearing in mind the differences in the temperature (170 and 300°C) at which the two investigations were carried out.     

Photooxidative and pyrolytic degradation of methyl methacrylate-alkyl acrylate copolymers

Different compositions of poly(methyl methacrylate-co-methyl acrylate) (PMMAMA), poly(methyl methacrylate-co-ethyl acrylate) (PMMAEA) and poly(methyl methacrylate-co-butyl acrylate) (PMMABA) copolymers were synthesized and characterized. The photocatalytic oxidative degradation of all these copolymers were studied in presence of two different catalysts namely Degussa P-25 and combustion synthesized titania using azobis-iso-butyronitrile and benzoyl peroxide as oxidizers. Gel permeation chromatography (GPC) was used to determine the molecular weight distribution of the samples as a function of time. The GPC chromatogram indicated that the photocatalytic oxidative degradation of all these copolymers proceeds by both random and chain end scission. Continuous distribution kinetics was used to develop a model for photocatalytic oxidative degradation considering both random and specific end scission. The degradation rate coefficients were determined by fitting the experimental data with the model. The degradation rate coefficients of the copolymers decreased with increase in the percentage of alkyl acrylate in the copolymer. This indicates that the photocatalytic oxidative stability of the copolymers increased with increasing percentage of alkyl acrylate. From the degradation rate coefficients, it was observed that the photocatalytic oxidative stability follows the order PMMABA > PMMAEA > PMMAMA. The thermal degradation of the copolymers was studied by using thermogravimetric analysis (TGA). The normalized weight loss and differential fractional weight loss profiles indicated that the thermal stability of the copolymer increases with an increase in the percentage of alkyl acrylate and the thermal stability of poly(methyl methacrylate-co-alkyl acrylate)s follows the order PMMAMA > PMMAEA > PMMABA. The observed contrast in the order of photostability and thermal stability of the copolymers was attributed to different mechanisms involved for the scission of polymer chain and formation of different products in both the processes.     

Thermal degradation of vinylidene chloride/[4-(t-butoxycarbonyloxy)phenyl]methyl acrylate copolymers

Vinylidene chloride polymers containing comonomer units capable of consuming evolved hydrogen chloride to expose good radical-scavenging sites might be expected to display greater thermal stability than similar polymers containing simple alkyl acrylates as comonomer. Incorporation of a comonomer containing the phenyl t-butyl carbonate moiety into a vinylidene chloride polymer has the potential to afford a polymer with pendant groups which might interact with hydrogen chloride to expose phenolic groups. Copolymers of vinylidene chloride with [4-(t-butoxycarbonyloxy)phenyl]methyl acrylate have been prepared, characterized, and subjected to thermal degradation. The degradation has been characterized by thermal and spectroscopic techniques. The degradation of vinylidene chloride/[4-(t-butoxycarbonyloxy)phenyl]methyl acrylate copolymers is much more facile than the same process for similar copolymers containing either [4-(isobutoxycarbonyloxy)phenyl]methyl acrylate or methyl acrylate, a simple alkyl acrylate, as comonomer. During copolymer degradation, [4-(t-butoxycarbonyloxy) phenylmethyl acrylate units are apparently converted to acrylic acid units by extensive fragmentation of the sidechain. Thus, the phenyl t-butyl carbonate moiety does function as a labile acid-sensitive pendant group but its decomposition in this instance leads to the generation of a phenoxybenzyl carboxylate capable of further fragmentation.     

Liquid Chromatographic Analysis of Styrene-Methacrylate and Styrene-Acrylate Copolymers

Abstract

Copolymers of styrene-methacrylate (methyl-, ethyl-, and n-butyl-) and styrene-acrylate (methyl-, ethyl-, and n-butyl-) were prepared by solution polymerization at a low degree of conversion. These copolymers were separated according to composition by liquid adsorption chromatography. Silica gel was the stationary phase and a mixture of chloroform and ethanol was the mobile phase. Ethanol content in the mobile phase affected the elution of the copolymers and methacrylate or acrylate rich copolymers required much ethanol to elute from a column. The retention of the copolymers was controlled by column temperature and the copolymers tended to retain in a column at higher column temperature. A linear gradient elution method way to increase ethanol in the mobile chase was effective to separate the copolymers in the order of increasing the methacrylate or acrylate content. Styrene rich copolymers eluted first from a column. Resolution between two adjacent peaks was improved with the increase in column temperature. In a mixture of copolymers of styrene-methacrylate or styrene-acrylate (methyl, ethyl, and n-butyl) having the same styrene content, the elution was in the order of n-butyl, ethyl, and methyl methacrylate or acrylate copolymers with styrene. In copolymrs having the same styrene content, a mixture of copolymrs having diffrent ester groups was separated and a mixtue of copolymrs having the same estr group (e.g., styrene-methyl mth-acrylate and styrene-methyl acrylate copolymers) was not separated.     

Two-Dimensional Chromatographic Analysis of Polystyrene-block-poly(methyl methacrylate) Copolymers Synthesized by Selective Oxidation of Polystrene-9-borabicyclo[3.3.1]nonane

Summary: The preparation of polystyrene block methyl methacrylate copolymers (PS-b-PMMA) is described. The polystyrene segment was prepared by anionic polymerization and the methylmethacrylate segment was prepared via free radical autoxidation of a borane agent attached to the styrene chain. 1 The chemistry involves a transformation of the anionic polymerization process to borane chemistry by firstly producing polystyrene with chain end unsaturated alkyl functional groups prepared using a n-butyllithium initiator and termination with allylchlorodimethylsilane. Secondly, the unsaturated macroinitiator end was hydroborated by 9-borabicyclo[3.3.1]nonane (9-BBN) to produce a borane terminated PS. Thirdly, the borane group at the chain end was selectively oxidized and converted to polymeric radicals in the presence of methyl methacrylate which then initiated radical polymerization to produce block copolymers. The polymer obtained was characterized using several chromatographic techniques including LC-CC (liquid chromatography under critical conditions) for the polystyrene segments and two-dimensional chromatography with LC-CC in the first dimension and SEC in the second. The results show that block formation was successful although significant homopolymerization of methyl methacrylate is also obtained.     

Side‐chain crystallization behavior of graft copolymers consisting of amorphous main chain and crystalline side chains: Poly(methyl methacrylate)‐graft‐poly(ethylene glycol) and poly(methyl acrylate)‐graft‐poly(ethylene glycol)

Graft copolymers consisting of amorphous main chain, poly(methyl methacrylate) (PMMA), or poly(methyl acrylate) (PMAc), and crystalline side chains, poly(ethylene glycol) (PEG), have been prepared by copolymerization of PEG macromonomers with methyl methacrylate or methyl acrylate (MMAx or MACx, respectively). Because of the compatibility of PMMA/PEG and PMAc/PEG, from small‐angle X‐ray scattering results, the main and side chains in graft copolymers were suggested to be homogeneous in the molten state. Differential scanning calorimetry (DSC) cooling scans revealed that PEG side chains for graft copolymers with large PEG fractions were crystallized when the sample was cooled, with a cooling rate of 10 °C/min. The spherulite pattern observed by a polarized optical microscope suggested the growth of PEG crystalline lamellae. Crystallization of PEG in MMAx was more restrained than in MACx. From these results, we have concluded that the crystallization behavior of the grafted side chains is strongly influenced by the glass transition of a homogeneously molten sample as well as dilution of the crystallizable chains. Domain spacings for isothermally crystallized graft copolymers were described by interdigitating chain packing in crystalline–amorphous lamellar structure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 79–86, 2005     

Thermal crosslinking of poly(methyl methacrylate) by reaction of methyl ester and quaternary ammonium salt and application to (meth)acrylate-based TPEs

Copolymers of N-vinylbenzyl N-methyl pyrrolidinium chloride (VBMPC) and methyl methacrylate, PVBMPC-co-poly(methyl methacrylate) (PMMA), were synthesized by free-radical copolymerization and proved to be prone to crosslinking as a result of the reaction of methyl ester groups with benzyl methyl pyrrolidinium chloride (BMPC) moieties at temperatures higher than 110 °C. When the VBMPC content was lower than 20 wt %, these copolymers were miscible with homo-PMMA. Blends of homo-PMMA and PVBMPC-co-PMMA fully could be cured above 150 °C, when the molecular weight of PMMA exceeded 10,000 and the VBMPC content of the copolymer was higher than 5 wt %. This reaction was carried out to crosslink selectively the PMMA microdomains of PMMA-b-poly(isooctyl acrylate) (PIOA)-b-PMMA (MIM) triblock copolymers to explain the mechanism for the mechanical failure of fully (meth)acrylic thermoplastic elastomers. Comparison of the ultimate tensile properties of MIM block copolymers, when the dispersed PMMA phases and PIOA matrix were crosslinked, led to the conclusion that the ductile failure of the hard PMMA microdomains rather than the elastic failure of the PIOA matrix was the reason for the mechanical failure of MIM triblocks. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4402–4411, 1999     

Quenching of photo-excited state of copolymer pendant Ru(bpy) complexes with methylviologen

Copolymer pendant tris(2,2′-bipyridine)ruthenium(II) complexes were prepared from the copolymers of 4-methyl-4′-vinyl-2,2′-bipyridine with styrene, acrylic acid, methyl methacrylate, hydroxyethyl methacrylate, acrylonitrile, N-vinylpyrrolidone, 4-vinylpyridine, and quaternized 4-vinylpyridine. The quenching of the photo-excited state of the polymer complexes by methylviologen was studied. Pendant anionic groups such as acrylate enhanced remarkably the quenching of the cationic sensitizer by the cationic substrate, however, pendant cationic groups such as quaternized pyridine did not affect the reaction. The polymer chain showed generally retarding effect on the quenching reaction.     

Linear polymers of allyl acrylate and allyl methacrylate

Allyl acrylate and allyl methacrylate were polymerized by anionic initiators to soluble linear polymers containing allyl groups in the pendant side chains. The pendant unpolymerized allyl groups of the resulting linear poly(allyl acrylates) were shown to be present by: (1) the disappearance of the acrylyl and methacrylyl double bond absorptions in the infrared spectra in the conversions of monomers to polymers; (2) postbromination of the allyl bonds in the linear polymer; (3) the disappearance of the allyl groups absorptions in the infrared spectra of the brominated linear polymers; and (4) the thermal- and radical-initiated crosslinking of the linear polymers through the allyl groups. Allyl acrylate and allyl methacrylate show great reluctance to copolymerize with styrene under anionic initiation, but copolymerize readily with methyl methacrylate and acrylonitrile. Block copolymers were prepared by reacting allyl methacrylate with preformed polystyrene and poly(methyl methacrylate) anions. The linear polymers and copolymers of allyl acrylate may be classified as “self-reactive” polymers which yield thermosetting polymers. Bromination of the linear polymers offers a convenient method of producing self-extinguishing polymers.     

Poly(methyl methacrylate) copolymers containing multiple,pendent plasticizing groups

New ether dimer (ED‐Eh) and diester (EHDE) derivatives of α‐(hydroxymethyl)acrylate, each having two 2‐ethylhexyl side chains, and an amine‐linked di(2‐ethylhexyl)acrylate (AL‐Eh), having three 2‐ethylhexyl side chains, were synthesized and (co)polymerized to evaluate the effects of differences in the structures of the monomers on final (co)polymer properties, particularly glass transition temperature, T_g. The free radical polymerizations of these monomers yielded high‐molecular–weight polymers. Cyclopolymer formation of ED‐Eh and AL‐Eh was confirmed by ¹³C NMR analysis and the cyclization efficiencies were found to be very high (～100%). Copolymers of ED‐Eh, EHDE, and AL‐Eh with methyl methacrylate (MMA) showed significant T_g decreases over poly(methyl methacrylate) (PMMA) due to 2‐ethylhexyl side groups causing “internal” plasticization. Comparison of the T_g's of the copolymers of 2‐ethylhexyl methacrylate, ED‐Eh, EHDE, and AL‐Eh with MMA revealed that the impacts of these monomers on depression of T_g's are identical with respect to the total concentration of the pendent groups. This is consistent with an earlier study involving copolymers of monomers comprising one and two octadecyl side groups with MMA. That is, the magnitude of decrease in T_g's was quantitatively related to the number of the 2‐ethylhexyl pendent groups in the copolymers rather than their placement on the same or randomly incorporated repeat units. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2302–2310, 2010