Photocatalytic degradation of methyl methacrylate copolymers

The photolytic and photocatalytic degradation of the copolymers poly(methyl methacrylate-co-butyl methacrylate) (MMA-BMA), poly(methyl methacrylate-co-ethyl acrylate) (MMA-EA) and poly(methyl methacrylate-co-methacrylic acid) (MMA-MAA) have been carried out in solution in the presence of solution combustion synthesized TiO₂ (CS TiO₂) and commercial Degussa P-25 TiO₂ (DP 25). The degradation rates of the copolymers were compared with the respective homopolymers. The copolymers and the homopolymers degraded randomly along the chain. The degradation rate was determined using continuous distribution kinetics. For all the polymers, CS TiO₂ exhibited superior photo-activity compared to the uncatalysed and DP 25 systems, owing to its high surface hydroxyl content and high specific surface area. The time evolution of the hydroxyl and hydroperoxide stretching vibration in the Fourier transform-infrared (FT-IR) spectra of the copolymers indicated that the degradation rate follows the order MMA-MAA > MMA-EA > MMA-BMA. The same order is observed for the rate coefficients of photocatalytic degradation. The photodegradation rate coefficients were compared with the activation energy of pyrolytic degradation. In degradation by pyrolysis, it was observed that MMA-BMA was the least stable followed by MMA-EA and MMA-MAA. The observed contrast in the order of thermal stability compared to the photo-stability of these copolymers was attributed to the two different mechanisms governing the scission of the polymer and the evolution of the products.     

Fluorescence of copolymers of 2-naphthyl methacrylate and methyl methacrylate

The fluorescence of a series of copolymers of 2-naphthyl methacrylate (2-NM) and methyl methacrylate (MMA) with various contents of 2-NM (obtained in chloroform, carbon tetrachloride and acetonitrile) was investigated. A linear dependence between the ratio of the excimer to monomer emission intensities (I_D/I_M) and the diad fraction (f_nn) of 2-NM monomer units was established. The relationship between I_D/I_M and f_nn · I_n (I_n = the mean sequence length of 2-NM units) fits a logarithmic curve. The results indicate that the excimer emission is determined mainly by the nearest neighbour naphthalene-containing monomer units in the copolymer chain. The copolymers obtained in acetonitrile have higher values of I_D/I_M than those obtained in chloroform and carbon tetrachloride. This difference is due to the higher content of mm-triads in copolymers from acetonitrile, confirmed by ¹H-NMR analysis of the samples of poly(methyl methacrylate) formed from copolymers of 2-NM and MMA.     

Thermal behaviour of copolymers of methyl methacrylate and 2-ethylhexyl methacrylate

Five copolymer samples containing different mole fractions of methyl methacrylate (MMA) and 2-ethylhexyl methacrylate (EHMA) were prepared by bulk polymerisation at 70°C using 0.2% benzoyl peroxide as an initiator. The copolymer composition was determined by¹H NMR spectroscopy. Molecular weight of copolymers was determined by gel permeation chromatography and viscosity measurements. Thermogravimetric experiments were conducted to evaluate activation energy for the degradation of copolymers. Two to four reaction stages for the weight loss were observed in the copolymers. A decrease in thermal stability was observed by an increase in EHMA content.     

Thermal behaviour of copolymers of methyl methacrylate and iso-octyl/iso-decyl methacrylate

Thermal behaviour of copolymers of methyl methacrylate (MMA) with iso-octyliso-decyl methacrylate was investigated using dynamic thermogravimetry, mass spectroscopy and pyrolysis gas chromatography. The copolymer samples were stable upto 250 °C. Total loss in weight was observed around 400 °C. The degradation in homopolymers as well as copolymers proceeded by predominans loss of monomer.

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Zusammenfassung Mittels dynamischer Thermogravimetrie, Massenspektroskopie und Pyrolysengaschromatographie wurde das thermische Verhalten von Kopolymeren aus Methylmethacrylat (MMA) und Isooktyl/Isodecyl-methacrylat untersucht. Die Kopolymerproben waren bis 250 °C stabil. Ein vollständiger Gewichtsverlust wurde bei 400 °C beobachtet. Der Abbau sowohl der Homopolymere als auch der Kopolymere erfolgt durch eine überwiegende Abgabe von Monomeren.

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, - /- . /- . 250°. 400°. , .

     

Photo-degradation of copolymers of methyl methacrylate and α-chloroacrylonitrile

Thin films of copolymers of methyl methacrylate (MMA) and α-chloroacrylonitrile (CAN) have been photolysed by 253·7 nm radiation under vacuum. Changes in molecular weight, the volatile products and the residual material have been examined. Most of the changes which occur can be accounted for in terms of the known reactions of the two homopolymers but the formation of small amounts of methyl chloride, the greater rate of formation of carbon dioxide in copolymers rich in CAN and the fact that unsaturated sequences in the polymer backbone involve MMA units are all evidence of interaction between the two types of unit during photolysis. All these features of the reaction are discussed from a mechanistic point of view.     

Conducting graft copolymers of pyrrole and thiophene with random copolymers of methyl methacrylate and 3-methylthienyl methacrylate

Random copolymers of 3-methyl thienylmethacrylate and methyl methacrylate were synthesized via free radical polymerization. Electro-copolymerizations of random copolymers with thiophene and/or pyrrole were carried out in acetonitrile-tetrabutylammonium tetrafluoroborate (TBAFB), water-p-toluene sulfonic acid (PTSA) solvent-electrolyte couples. Oxidative polymerization of thiophene functionalized random copolymer was also achieved by constant current electrolysis and chemical polymerization. The characterizations were done by conductivity measurements, cyclic voltammetry (CV), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermal gravimetry analysis (TGA), scanning electron microscopy (SEM).     

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.     

Pyrolysis—gas chromatography of methyl methacrylate—styrene and methyl methacrylate—α-methylstyrene copolymers

The pyrolysis—gas chromatographic behaviour of methyl methacrylate copolymers with styrene or α-methylstyrene was investigated with a Curie-point pyrolyzer. Monomer yield from each copolymer was very high as a result of the high probability of unzipping. Though only small quantities of dimers and or trimers are formed on the pyrolysis of two copolymers, they reflect the sequence distribution of copolymers. Under some assumption, the run number of each copolymer is calculated using the amounts of dimer and or trimer formed.     

Adhesion of methyl methacrylate copolymers to silicate glass

Adhesion of methyl methacrylate copolymers with acrylic acid, methacrylic acid, and methacrylamide to silicate glass was studied. The copolymers of methyl methacrylate with acrylic and methacrylic acids, compared to poly(methyl methacrylate), are characterized by higher adhesion strength of polymer fi lm-silicate glass joints.     

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.     

Preparation and characterization of copolymers of chloroprene and methyl methacrylate

The preparation of chloroprene–methyl methacrylate copolymers in the presence of Lewis acids (Et_1.5AlCl_1.5) in hydrocarbon solvent and the effect of Lewis acids concentration on copolymer composition are described. ¹³C NMR spectra were obtained on these copolymers. In samples of high MMA content, tactic placements of MMA were observed as well as several different kinds of sequences for chloroprene and MMA. In samples of low MMA content, no tactic placements of MMA were found but several different kinds of chloroprene sequences were observed. From the analysis of the ¹³C NMR spectra of the different copolymers examined, it is apparent that all the various kinds of chloroprene sequences in these copolymers can be determined.     

Preparation and degradation of copolymers of methyl methacrylate with alkali metal methacrylates—I. Copolymerization parameters for the systems methyl methacrylate-lithium methacrylate,methyl methacrylate-sodium methacrylate and methyl methacrylate-potassium methacrylate

Copolymerizations of methyl methacrylate with the Li, Na and K salts of methacrylic acid have been studied in methanol solution at 60°. Reactivity ratios have been calculated by the methods due to Mayo and Lewis, Fineman and Ross and Peckham. The rate of copolymerization decreases as the size of the metal cation increases, in contrast to the behaviour in the homopolymerization of the alkali metal methacrylates. The systems have the following reactivity ratios (MMA as monomer-1): Li salt r₁ = 0.59, r₂ = 0.073; Na salt r₁ = 3.97, r₂ = 0·126; K salt r₁ = 5.65, r₂ = 0.143. The MMA-LiMA system shows azeotropic copolymerization for a mole fraction of MMA in the feed equal to 0.7. This system shows a strong tendency towards alternation (r₁r₂ = 0.044). The differences in the reactivity ratios are discussed in relation to steric and electrostatic effects.     

Living anionic polymerization of lauryl methacrylate and synthesis of block copolymers with methyl methacrylate

Anionic polymerization of lauryl methacrylate (LMA) with 1,1‐diphenylhexyl lithium in tetrahydrofuran (THF) at ?40 °C resulted in a multimodal and broad molecular weight distribution (MWD) with poor initiator efficiency. In the presence of additives such as dilithium salt of triethylene glycol (G₃Li₂), LiCl, and LiClO₄, the polymerization resulted in polymers with a narrow MWD (≤ 1.10). Diblock copolymers of methyl methacrylate (MMA) and LMA were synthesized by anionic polymerization using DPHLi as initiator in THF at ?40 °C with the sequential addition of monomers. The molecular weight distribution of the polymers was narrow and without homopolymer contamination when LMA was added to living PMMA chain ends. Diblock copolymers with broad/bimodal MWD were obtained with a reverse‐sequence monomer addition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 875–882, 2004     

Characterization of azo-containing polydimethylsiloxanes and their copolymers with methyl methacrylate

Azo group-containing polydimethylsiloxanes (PDMS–ACP), macroazoinitiators, were prepared by polycondensation reaction of 4,4′-azobis-4-cyanopentanoyl chloride (ACPC) with hydroxybutyl-terminated polydimethylsiloxane (PDMS) of varying molecular weights. The activation energy (E_a), activation enthalpy (ΔH^‡), and activation entropy (ΔS^‡) of the thermodecomposition of PDMS-ACP in toluene increased with increase in poly-dimethyl-siloxane chain length (SCL) in PDMS moieties, while the activation free energy (ΔG^‡) was independent on the SCL. The polydimethylsiloxane-poly(methyl methacrylate) block copolymers (PDMS-b-PMMA) were prepared by the use of PDMS-ACP macroazoinitiators, and they were characterized by ¹H-, ²⁹Si-, and ¹³C-nuclear magnetic resonance (NMR) spectroscopies. The microstructure and morphology of copolymers were investigated by proton spin–spin relaxation measurements and scanning electron microscopy (SEM). © 1996 John Wiley & Sons, Inc.     

Photodegradation in solution of copolymers of methyl vinyl ketone and methyl isopropenyl ketone with methyl methacrylate

Copolymers of methyl vinyl ketone (MVK) and methyl isopropenyl ketone (MIK) with methyl methacrylate (MMA), have been prepared covering the whole composition range. Reactivity ratios have been estimated as follows: MMA/MVK, r_MMA = 0·63 ± 0·2, r_MVK = 0·53 ± 0·2; MMA/MIK, r_MMA = 0·98 ± 0·2, r_MIK = 0·69 ± 0·2. Number average molecular weights have been measured during the course of photodegradation under 253·7 nm radiation in methyl acetate solution and rates of chain scission calculated. In each system the copolymers are less stable than the corresponding homopolymers, the rate passing through a maximum at 20–30% ketone content. These results have been discussed from a mechanistic point of view.     

Self-assembly of monodisperse polymer microspheres from PPQ-b-PEG rod-coil block copolymers inselective solvents

Self-assembly of macromolecules is a new fastdeveloping research field in recent years. So far it hasbeen known that many different forms and orderedfunctional nanometer materials, nanometer structurematerials and ordered porous materials are obtained bys…     

Dielectric study of side-group rotation of methyl methacrylate in copolymers

The dielectric absorption due to the side-group rotation of the methyl methacrylate (MMA) unit in MMA-styrene and MMA-p-chlorostyrene (pCS) copolymers was measured. The relaxation time for MMA-pCS copolymers with low MMA contents could be interpreted quantitatively in terms of the Kramers rate-constant theory at the low-friction limit. On the other hand, the frictional effect on the relaxation time could not be ignored for any copolymers except for the MMA-pCS copolymers with low MMA contents. The relaxation time for pure poly(methyl methacrylate) could be interpreted by the Kramers theory at the high-friction limit.     

Synthesis and characterization of miniemulsion copolymers of methyl methacrylate (or styrene) and stearyl methacrylate

The copolymers of methyl methacrylate (MMA) (or styrene (ST))/stearyl methacrylate (SMA) obtained from miniemulsion polymerization were prepared and characterized. All the miniemulsions showed satisfactory colloidal stability upon aging due to the effectively retarded Ostwald ripening by the reactive costabilizer SMA. In subsequent miniemulsion copolymerizations, monomer droplet nucleation predominated in the particle formation process, but homogeneous nucleation could not be ruled out even at such high levels of SMA (20–50 wt.%). The contact angle first increased rapidly and then leveled off when the SMA content increased from 20 to 50 wt.% for both the copolymers of MMA/SMA and ST/SMA. At constant level of SMA, the copolymer of MMA/SMA with a less hydrophobic composition showed a larger contact angle compared to the ST/SMA counterpart. The contact angle (103 ± 1°) of the copolymer MMA/SMA (50/50 w/w) was comparable to that (104°) of PSMA. A schematic model was proposed to explain the experimental results.