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.     

Thermal degradation of phenyl methacrylate-methyl methacrylate copolymers

The degradation behaviours of poly(phenyl methacrylate), four phenyl methacrylate-methyl methacrylate copolymers which span the composition range, and poly(methyl methacrylate) have been compared by using thermogravimetry in dynamic nitrogen and thermal volatilisation analysis (TVA) under vacuum, with programmed heating at 10°C/min. Volatile products have been separated by subambient TVA and identified and the cold ring fraction and partially degraded polymer have been examined by ir spectroscopy. Poly(phenyl methacrylate) resembles poly(methyl methacrylate) in degrading completely to monomer. Copolymers of phenyl methacrylate and methyl methacrylate are more stable than the homopolymers. On degradation, the major products are the two monomers. Minor products from all the copolymers include carbon dioxide, dimethylketene, isobutene and formaldehyde. Copolymers with low and moderate phenyl methacrylate contents show the formation of anhydride ring structures in the cold ring fraction and partially degraded copolymer, together with small amounts of methanol in the volatile products. Carbon dioxide is a more significant product at lower phenyl methacrylate contents.The mechanism of degradation is discussed.     

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.     

Thermal degradation of phosphonated poly(methyl methacrylate)

On heating at volatilisation temperatures, poly(methyl methacrylate) (PMMA) and diethoxyphosphonated poly(methyl methacrylate) (Ph.PMMA) behave differently in the very early stage of the degradation process. The volatilisation rate of PMMA decreases slowly with conversion whereas Ph.PMMA polymers volatilise at a high initial rate which decreases quickly with conversion.The overall volatilisation rate of Ph.PMMA polymers in this stage is much lower than that of PMMA. This is attributed to the formation of anhydride in degrading Ph.PMMA by intramolecular cyclisation which forms high boiling chain fragments.     

Photopolymerizations initiated by oxime derivatives

A number of ester, urethane, and carbonate derivatives of biacetyl monooxime, dimethylglyoxime, and ketone oxime, were synthesized and their photolyses studied by means of ultraviolet spectroscopy. Most of the oxime derivatives photolyzed easily upon UV irradiation. Among them, however, only the free radicals formed by photolysis from the ester and carbonate of biacetyl monooxime could effectively initiate the polymerization of a vinyl monomer such as methyl methacrylate. Based on the results obtained from the monomeric reactions, syntheses of grafting polymers were made. Graft polymers were obtained by using a copolymer of methyl methacrylate and methacrylic acid–biacetyl monooxime ester (copolymer I) and that of methyl methacrylate and vinyl benzioc acid–biacetyl monooxime ester (copolymer II) in good yield and without the formation of homopolymer. It was also found that when copolymer I was employed as a grafting polymer, a considerable amount of main-chain scission was seen, but no chain degradation was noted in the case of copolymer II. Photocrosslinking was attempted by using these copolymers in the presence of divinyl benzene. It was confirmed that copolymer II was photocrosslinkable, whereas copolymer I underwent photodegradation.     

Free-radical multicomponent polymerization reactors and chemical composition distribution

Formulae to calculate the statistically caused instantaneous copolymer composition distribution as well as the chemical distribution of accumulated macromolecules, which is due to polymerization statistics and shifts in mean polymer composition during the reaction process, are derived on the basis of a universal model for free-radical solution polymerization with any number of monomers proceeding in a batch, semi-batch or continuous, ideally mixed vessel. The influence of the reactor type on chemical composition distributions is investigated for a copolymerization of different reactive components (methyl methacrylate/styrene/maleic anhydride), a system with nearly equal reactive monomers (methyl methacrylate/styrene), and the ternary polymerization of methyl methacrylate/styrene/maleic anhydride. Though products of constant mean composition are obtainable in a semi-batch or steady-state continuous reactors, considerable statistical dispersion cannot be removed in any case.     

Effect of the initial maleic anhydride content on the grafting of maleic anhydride onto isotactic polypropylene

A series of ¹³C‐enriched maleic anhydride grafted isotactic polypropylene samples were prepared in solution at 170 °C by changes in the initial maleic anhydride content. The NMR spectra of the samples showed that the signals of the maleic anhydride attached to the tertiary carbons of the isotactic polypropylene chains increased considerably with increasing maleic anhydride content, whereas the signals of the maleic anhydride on the radical chain ends (with a single bond) arising from β scission did not. On the other hand, the signals of the maleic anhydride on the radical chain ends with double bonds increased markedly with increasing maleic anhydride content, and this suggested that β scission could occur extensively after maleic anhydride was attached to the tertiary carbons. As a result, the molecular weight of the grafted polypropylene decreased significantly with increasing maleic anhydride content in this study. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5529–5534, 2005     

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.     

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.     

Kinetic analysis of the oxidative degradation of polyaryl-orthophosphate

Summary Thermogravimetric study of poly-aryl-orthophosphate indicates that in presence of air the decomposition is a two step process. The first step is the chain scission to form quinone and the subsequent step the oxidation of quinone to maleic anhydride. The kinetic parameters were determined for the oxidative thermal degradation process.With 4 figures     

Influence of reactor operational policies on distributions of chemical composition,molar mass,sequence length and sequence frequency of multicomponent polymers obtained by free-radical polymerization

Remarkable shifts in chemical composition, molar mass, sequence length and sequence frequency will occur in the course of free-radical multicomponent polymerizations, if the reactivities of the comonomers are different and a simple batch reactor is used. It is shown for the terpolymerization system of methyl methacrylate/styrene/maleic anhydride that a semi-batch reactor with appropriate regimes is suitable to obtain products with improved chemical, molecular and sequential homogeneity. However, if polymers with defined inhomogeneities like bimodal molar mass or chemical composition distributions are desired, these are also obtainable by use of appropriate operational policies, which will be illustrated for the homopolymerization of methyl methacrylate and the binary copolymerization of methyl methacrylate/maleic anhydride. Concerning the instantaneous mean chemical composition of polymer molecules, which cannot be measured directly, a new procedure is presented to determine this quantity experimentally.     

Polymerization of methyl methacrylate in a tetrahydrofuran–maleic anhydride system. Part II

A donor–acceptor complex consisting of tetrahydrofuran and maleic anhydride initiates photochemical and thermal polymerization of methyl methacrylate. The mechanism of the transformation of this complex was investigated by studying changes in its electrical conductivity, its chemiluminescence, and various influences on its initiating capability (water, air, DPPH, substitution of styrene for methyl methacrylate and of 1,4-dioxane for tetrahydrofuran). It has been shown that initiation by radicals cannot be clearly excluded and that ionic radicals form in the system and can initiate the anionic growth of the chain.     

Radiation degradation susceptibility of vinyl polymers: Nitriles and anhydrides

The effect of γ irradiation on a series of vinyl polymers, which included polymethacrylonitrile, poly(α-chloroacrylonitrile), poly(dimethyl itaconate), poly(acrylic anhydride), and poly(methacrylic anhydride), was studied as part of a program to develop improved positive lithographic resists. Radiation-induced degradation was observed for polymethacrylonitrile, poly(α-chloroacrylonitrile), and poly(methacrylic anhydride). Molecular weight degradation as a function of dose was monitored by membrane osmometry or GPC techniques. For γ-irradiated poly(dimethyl itaconate) and poly(acrylic anhydride) crosslinking was found to predominate over chain scission. [G(s)–G(x)] values, calculated from molecular weight inverse versus dose curves, indicate that both nitrile polymers degraded more efficiently than a poly(methyl methacrylate) reference standard on the basis of M _n changes. The radiation behavior of the first three polymers confirms earlier findings than vinyl polymers with quaternary carbons predominantly degrade when subjected to ionizing radiation.     

Polymerization behavior of bistrimethylsilyloxycycloalkenes

The radical copolymerizations of bistrimethylsilyloxycycloalkenes, such as 1,2-bistrimethylsilyloxycyclobutene (I), 1,2-bistrimethylsilyloxycyclopentene (II), and 1,2-bistrimethylsilyloxycyclohexene (III), were carried out with acceptor monomers, such as maleic anhydride, N-phenylmaleimide, and methyl methacrylate. I and II gave alternating copolymers with maleic anhydride and random copolymers with N-phenylmaleimide but no copolymer with methyl methacrylate. III gave no copolymer with the acceptor monomers. These polymerization behaviors of bistrimethylsilyloxycycloalkenes were explained primarily in terms of the electron donor–acceptor interaction between both monomers.     

Preparation and degradation of salts of poly(methacrylic acid)—Part II: Magnesium,calcium, strontium and barium salts

The thermal degradation behaviour of the alkaline earth metal polymethacrylates has been compared with that of the corresponding acetates and that of the alkali metal polymethacrylates, using thermal volatilisation analysis, thermogravimetry and analysis of the several product fractions and partially degraded polymer. The salt polymers resemble the acetates only in the order of their stabilities which increase with the size of the metal ion. Chain scission and depolymerisation, which was found to be an important process in the alkali metal polymethacrylate series, cannot occur to the same extent in the alkaline earth metal series because, except in the case of the magnesium salt, the monomers are involatile and cannot distil out of the reaction zone. The alternative process, involving formation of ketones and metal carbonate or oxide, therefore predominates. There is some evidence that chain scission occurs in the case of magnesium polymethacrylate. The mechanism of degradation is discussed.     

蓖麻油—甲基丙烯酸甲酯AB交联聚合物的研究

将蓖麻油与顺丁烯二酸酐反应,合成端乙烯基蓖麻油,再与甲基丙烯酸甲酯共聚,制得了组成不同的一系列AB交联聚合物,研究了它们的动态性能、力学性能和形态结构与组成的关系.     

Resist polymers: Part IX—Thermolysis of chlorine-containing acrylate polymers

The thermal degradation of poly(chloroethyl methacrylate) (PCEMA), poly(trichloroethyl methacrylate) (PTCEMA), poly(methyl-α-chloroacrylate) (PMCA) and their copolymers with methyl methacrylate (MMA) has been investigated. Both ester decomposition and main chain scission occur for the chloroalkyl methacrylate polymers with the former playing the dominant role. In contradistinction, HCl elimination and aromatization prevail over other processes for PMCA. The thermolysis results are compared with radiolysis results.     

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.     

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.     

Quantitative analysis of random scission and chain-end scission in the thermal degradation of polyethylene

The thermal degradation of polyethylene includes two different kinds of pathways. These are random and chain-end scissions which include β-scission on the chain end and radical transfer scission. We conducted a quantitative analysis on these pathways by Pyrolysis-GC/MS and computer simulation. Two different distributions of scission products of polyethylene were observed at different temperatures. They are determined by the relationship between rate of reaction and that of volatilisation. Furthermore, a characteristic distribution was observed in lower molecular weight. It could be explained by direct scission and one to five-step radical transfer scissions. The pathway possibilities calculated with the accumulated schemes showed that the direct scission and one-step-radical transfer increased with the temperature. This indicates that β-scission occurs on the chain end before the radical transfer because the rate of the β-scission becomes faster as the temperature rises.