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.     

Thermal analysis of blends of low density polyethylene, poly(ethyl acrylate) and ethylene ethyl acrylate copolymer with polydimethylsiloxane

The thermal stability of blends of polyethylene, poly(ethyl acrylate) and ethylene ethyl acrylate (EEA) copolymer with polydimethylsiloxane has been investigated in inert atmosphere using TG-DTC and TVA. The condensable volatile degradation products from the TVA experiments were separated by subambient TVA and investigated by FT-IR spectroscopy, GC., MS and GCMS techniques. The cold ring fraction was characterised by FT-IR spectroscopy and GC. Most of the degradation products from the blends were similar to the degradation products from polydimethylsiloxane and the corresponding polyolefin when degraded alone, but the presence of some additional products indicated interactions during degradation as a result of blending. The mechanisms of formation of degradation products from the blends are discussed in detail.     

Thermal degradation of poly(vinyl bromide), vinyl bromide-methyl methacrylate copolymers,and poly(vinyl bromide)-poly(methyl methacrylate) blends

Degradation behavior has been compared for PVB, five VB-MMA copolymers which span the composition range, PMMA, and PVC by using thermogravimetry in dynamic nitrogen and thermal volatilization analysis (TVA) under vacuum for programmed heating at 10°C/min. Volatile products have been separated by subambient TVA and identified. PVB is substantially less stable than PVC but shows inmost respects analogous degradation behavior. The introduction of VB into the PMMA chain leads to intramolecular lactonization with release of methyl bromide at temperatures a little above 100°C; after this reaction is complete, however, the polymer is more stable toward volatilization than PMMA. Copolymers with moderate and high VB contents also lose hydrogen bromide. Carbon dioxide is a significant product at intermediate compositions. The variation of product distribution with copolymer composition is discussed in relation to the several reactions involved and comparisons are made with VC-MMA copolymers. PVB-PMMA blends snow some features of degradation behavior in common with the PVC-PMMA system but also very important differences. The effect of PVB is only to stabilize the PMMA; the mechanism is discussed. The role of PVB as an additive and VB as a comonomer for fire-retardant PMMA compositions is briefly considered in relation to earlier studies.     

Preparation and degradation of copolymers of methyl methacrylate with alkali metal methacrylates—II: Thermal analysis of the copolymers,nature of the degradation products and general characteristics of the degradation reaction

Three series of copolymers, each spanning the composition range from alkali metal methacrylate homopolymer to methyl methacrylate homopolymer, have been prepared; their degradations have been studied under programmed heating conditions, by means of simultaneous thermogravimetry and thermal volatilization analysis (TVA) in a vacuum system and by differential thermal analysis in dynamic nitrogen. Total volatile products have been characterised by infrared spectroscopy, subambient TVA and GLC. The thermal analysis data suggest that the two types of monomer unit tend to participate in degradation processes in different temperature ranges. However, in addition to those products characteristic of the degradation of each homopolymer, the copolymers give substantial amounts of methanol; this product must arise from a reaction specific to the copolymer structure.     

Thermal and photo induced reactions in blends of polypropylene and poly(methyl methacrylate)

Thermal Volatilization Analysis (TVA) demonstrates that poly(methyl methacrylate) (PMMA) is stabilized by blending with polypropylene (PP). Although well-defined radical reactions occur in both polymers under 2537 Å radiation, there is no evidence of the formation of block or graft copolymers when blends of the two are irradiated. Preirradiation suppresses the amount of monomeric methyl methacrylate formed on subsequent thermal degradation. The missing methyl methacrylate units appear in the chain fragment fraction. The characteristics of the thermal degradation of blends of unirradiated PP with preirradiated PMMA are similar to those of unirradiated rather than pre-irradiated blends, thus emphasizing the importance of the PP component in determining the thermal stability of blends after irradiation. These observations are discussed mechanistically.     

Thermal degradation of bromine-containing polymers: Part 10—Copolymers of 2,3-dibromopropyl methacrylate and 2,3-dibromopropyl acrylate with methyl acrylate

The products of the thermal degradation of copolymers of methyl acrylate (MA) with 2,3-dibromopropyl methacrylate (2,3-DBPM) and 2,3-dibromopropyl acrylate (2,3-DBPA) have been analysed quantitatively using thermal analysis, infra-red spectroscopy, mass spectrometry and gas-liquid chromatography. The dominant products from the first of these systems are 2,3-DBPM monomer and chain fragments reflecting the behaviours of the homopolymers of 2,3-DBPM and MA, respectively. The yield of methyl bromide is at a maximum when the proportion of interunit bonds between the two monomers is at a maximum. From the second system, the dominant products are methyl bromide and the chain fragment or cold ring fraction. The mechanisms by which these and the many other products are formed are discussed with reference to related systems which have been studied previously.     

Thermal degradation of blends of polystyrene and poly-4-methoxystyrene with bisphenol A polycarbonate

Blends of polystyrene (PS) and poly-4-methoxystyrene (PMeS) with bisphenol A polycarbonate (PC) (1:1 by weight) have been studied using thermogravimetry (TG) and thermal volatilisation analysis (TVA). The condensable volatile products obtained in the TVA experiments were separated by subambient TVA and the less-volatile liquids were examined by GC-MS. The cold ring fraction of products was characterised by IR spectroscopy.

On degradation, both PS-PC and PMeS-PC blends show an interaction which is observed as a destabilisation. It is suggested that in the degrading blends, the PC component is destabilised as a result of transport of small radical species from the other polymer phase. These radicals may abstract hydrogen atoms, leading to an increase in backbone scission reactions and consequently a lower degradation temperature than when the polymer is degraded alone.     

The structure and stability of oxidised polybutadiene

Polybutadiene has been oxidised at 0–20°C for periods from one day up to several months and also at elevated temperatures. Microstructural changes in the polymer due to oxidation have been followed by ir and uv spectroscopy. Oxidised samples of the polymer have been degraded in nitrogen or in vacuum under programmed heating conditions by TG, DSC and thermal volatilisation analysis (TVA). In TVA degradations, non-condensable gaseous products have been studied by adsorption TVA, condensable volatile products have been separated by subambient TVA for identification, cold ring fraction materials have been examined spectroscopically and the ir spectrum of the polymer residue, after degradation to 440°C, has also been obtained. From this considerable amount of data it has been possible to propose structures present in oxidised polybutadienes and to suggest some degradative processes involved in the subsequent thermal degradation. Oxidation leads to a considerable lowering of the threshold temperature for the main decomposition process; in samples oxidised at low temperatures, an additional early stage of degradation, commencing near 100°C, is found, due to peroxide decomposition.     

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.     

Ionic-conductivity switching of vinyl malachite green leuconitrile copolymers based on photoinduced carrier generation

Copolymers of bis[4-(N,N-dimethylamino)phenyl]-4-vinylphenylmethanenitrile (vinyl Malachite Green leuconitrile) with methyl methacrylate or ω-methoxyoligo(oxyethylene) methacrylate have been synthesized, aiming at designing one-component-type organic polymers for photoswitchable ion-conducting films. The triphenylmethanenitrile copolymers with ω-methoxyoligo(oxyethylene) methacrylate were found to undergo ionic-conductivity switching by turning on and off UV light at ambient temperature, owing to their low glass transition temperature. © 1993 John Wiley & Sons, Inc.     

Thermal degradation of ammonium polymethacrylate and polymethacrylamide

The degradation of ammonium polymethacrylate and polymethacrylamide has been studied by a combination of thermal analysis methods (TVA and TG) and examination of volatile and involatile products by infrared analysis. It is shown that total reaction comprises an initial cyclization and further fragmentation of the modified chain at higher temperatures to yield gaseous volatiles. The partially degraded NH₄PMA contains anhydride ring and cyclic imide structures in the chain. Quantitative comparison of yields of isocyanic acid and carbon dioxide has shown that imidization is the major reaction and anhydride formation is of less importance. The mechanisms of the various reactions are discussed.     

Synthesis and radiation degradation of vinyl polymers with fluorine: Search for improved lithographic resists

Homopolymers of methyl α-fluoroacrylate (MFA), trifluoroethyl methacrylate (TFEM), and hexafluoroisopropyl methacrylate (HFIM) were prepared, as were their methyl methacrylate (MMA) copolymers. Copolymers of vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE) with MMA were also prepared. The radiation susceptibilities of these polymers were measured by the ⁶⁰Co γ-irradiation method, in which molecular weights were measured by membrane osmometry and gel permeation chromatography (GPC). All the copolymers degraded by predominant chain scission except poly(methyl α-fluoroacrylate), (PMFA), which crosslinks even at low doses (ca. 1 Mrad). The G_s - G_x and G_s values of the chain scissioning polymers and copolymers are higher than those of poly(methyl methacrylate) PMMA reference. The high susceptibility of PMFA homopolymer to crosslinking is in contrast to that of poly(methyl α-chloroacrylate), as we reported earlier. This effect is interpreted as resulting from extensive hydrogen fluoride and polyenlyl radical formation, which leads to facile crosslinking. However, incorporation of the MFA monomer unit causes the (22/78) MFA/MMA copolymer to degrade with a larger value of G_s that PMMA. Apparently a second-order process leads to crosslinking in PMFA and this is retarded in the copolymer. In the hehomopolymers of HFIM and TFEM and in the HFIM-MMA and TFEM-MMA copolymers the HFIM and TFEM components facilitate degradation with negligible crosslinking. The increased degradation susceptibility of VDF and CTFE copolymers with MMA over that of PMMA is attributed to processes at the VDF or CTFE components present in smaller concentrations (3-5 mole %) than the threshold levels (25-50% necessary for significant crosslinking).     

Thermal degradation behavior of blends of phenyl methacrylate-styrene copolymers with aluminum isopropoxide

Thermal degradation studies were carried out of copolymer phenyl methacrylate-styrene in the presence of aluminum isopropoxide to assess the stability and alteration of degradation mechanism using thermogravimetry-differential thermogravimetry (TG-DTG) in inert atmosphere and under vacuum using thermal volatilization analysis (TVA). After collecting the condensable volatile degradation products from TVA experiments and separating them by sub-ambient TVA, investigation and identification were effected out by IR spectroscopy and gas chromatography-mass spectrometry (GC-MS) techniques. The degradation products from the blends consisted of some additional products, i.e., isopropanol, phenol, methacrylic acid, ethyl benzene, benzene and a cyclic compound apart from similar products obtained from the degradation of pure copolymers. The mechanism of newly formed degradation products has been discussed in detail. This revised version was published online in August 2006 with corrections to the Cover Date.     

Preparation and thermal degradation of methyl methacrylate-methacrylic acid copolymers

Copolymers of methyl methacrylate with methacrylic acid, with the mole fraction of methacrylic acid units from 0.21 to 0.73, were prepared by radical copolymerization in the bulk. The influence of the composition of the copolymers on the features of their thermal degradation was examined by combined thermal analysis involving differential scanning calorimetry and thermogravimetry.     

Aggregation and protein binding of sodium maleate copolymers with varying hydrophobicities

Copolymers of sodium maleate with methyl methacrylate, styrene, or vinyl acetate have been synthesized and studied in aqueous NaCl solutions of various ionic strengths. The polymers are polyelectrolytes with varying hydrophobicities, and their solution properties have been studied using static and dynamic light scattering. Copolymers containing methyl methacrylate or styrene were shown to aggregate in water upon increasing salt concentration. Copolymers of sodium maleate and vinyl acetate do not associate with increasing ionic strength. The binding of bovine serum albumin and cytochrome C to the sodium maleate copolymers was also investigated by light scattering. It was observed that cytochrome C forms complexes with the copolymers containing methyl methacrylate or vinyl acetate whereas albumin does not bind to any of the copolymers studied. Copyright © 2004 John Wiley & Sons, Ltd.     

Radiation degradation of copolymers of methyl methacrylate and 3-oximino-2-butanone methacrylate

Copolymers of methyl methacrylate and 3-oximino-2-butanone methacrylate (OM) were investigated as deep-UV and e-beam resists. Their increased sensitivity relative to PMMA (up to 50 times) was correlated with the radiation chemical yields of the volatile products and main chain scissions. The degradation of these copolymers, activated by the 3-oximino-2-butanone entity, is discussed in terms of energy absorption mechanisms and the subsequent scission reactions.     

Compatibilizing effect of a graft copolymer on bacterial poly(3‐hydroxybutyrate)/poly(methyl methacrylate) blends

Blends of isotactic (natural) poly(3‐hydroxybutyrate) (PHB) and poly(methyl methacrylate) (PMMA) are partially miscible, and PHB in excess of 20 wt % segregates as a partially crystalline pure phase. Copolymers containing atactic PHB chains grafted onto a PMMA backbone are used to compatibilize phase‐separated PHB/PMMA blends. Two poly(methyl methacrylate‐g‐hydroxybutyrate) [P(MMA‐g‐HB)] copolymers with different grafting densities and the same length of the grafted chain have been investigated. The copolymer with higher grafting density, containing 67 mol % hydroxybutyrate units, has a beneficial effect on the mechanical properties of PHB/PMMA blends with 30–50% PHB content, which show a remarkable increase in ductility. The main effect of copolymer addition is the inhibition of PHB crystallization. No compatibilizing effect on PHB/PMMA blends with PHB contents higher than 50% is observed with various amounts of P(MMA‐g‐HB) copolymer. In these blends, the graft copolymer is not able to prevent PHB crystallization, and the ternary PHB/PMMA/P(MMA‐g‐HB) blends remain crystalline and brittle. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1390–1399, 2002     

Thermal degradation of polycarbonate-poly(methyl methacrylate) blends by thermal volatilisation analysis

The degradation of bisphenol A polycarbonate (PC), poly(methyl methacrylate) (PMMA) and a 1:1 by weight blend of PC and PMMA have been studied by thermogravimetry, thermal volatilisation analysis and differential scanning calorimetry. Volatile products have been investigated and separated by subambient TVA and characterised spectroscopically. In the degradation of the blend, no change is observed in the nature of the volatile products of degradation, but the rate of degradation of the PC component is increased and the PMMA depolymerisation is retarded. It is suggested that PMMA radicals attack PC macromolecules leading to chain scission in the PC at lower temperatures than required for homolysis in pure PC. This unusual form of interaction involving a macroradical and a macromolecule is made possible by the homogeneous character of the molten blend.     

Influence of the fire retardant,ammonium polyphosphate,on the thermal degradation of poly(methyl methacrylate)

The thermal degradation of ammonium polyphosphate (APP), a commercial fire retardant, and its blends with poly(methyl methacrylate) (PMMA) have been studied by thermal volatilization analysis (TVA) and the degradation products identified. APP degrades under vacuum in three stages. Initially it condenses to an ultraphosphate (<260°C) with release of ammonia and water. Fragmentation follows (260–370°C), giving high-boiling ammonium salts of phosphate fragments and further ammonia and water. The polyphosphoric acid (PPA) which remains then undergoes extensive Fragmentation (>370°C). In the presence of APP, the normal depolymerization of PMMA to monomer competes with degradation reactions which form high-boiling chain fragments, methanol, carbon monoxide, dimethyl-ether, carbon dioxide, hydrocarbons, and char. These additional reactions are initiated principally by the PPA. Intramolecular cyclization occurs, resulting in the formation of anhydride, and ester groups are eliminated, methanol and carbon monoxide being evolved. Further degradation of the modified polymer leads to the other volatile products and the char.