Synthesis of monodisperse submicron spherical poly(methylmethacrylate) particles and the molecular dynamics simulation

The molecular-dynamics method has been used to determine the conformational states of poly(methyl methacrylate) chains in a medium composed of water and a monomer (methyl methacrylate). Experimentally detected spherical particles resulting from polymerization have been found to take the form of droplet-type aggregates containing several chains, with the water and monomer concentrations in the aggregates differing from those in the dispersion medium. It has been shown that the methyl methacrylate concentration in an initial reaction mixture of about 20% is optimal for the formation of spherical droplet-type aggregates. It has been experimentally established that spherical poly(methyl methacrylate) particles with a narrow size distribution are formed at a methyl methacrylate concentration of ≈23%.     

Compatibility studies on solutions of polymer blends by viscometric and ultrasonic techniques

Detailed viscometric and ultrasonic velocity studies have been conducted on solutions of blends of poly(methyl methacrylate) with poly(vinyl acetate), poly(vinyl chloride) with poly(vinyl acetate) and poly(methyl methacrylate) with polystyrene over an extended range of concentrations and temperatures in toluene, chlorobenzene and toluene respectively. The plots of both absolute viscosity and ultrasonic velocity vs composition deviate from linearity according to the degree of compatibility of polymer blends, at all concentrations and temperatures. The curves for compatible systems are linear. These investigations offer an entirely new approach to the study of the compatibility of polymer blends.     

Formation of a linear-polyurethane-linear-polystyrene blend in situ

Blends of linear poly(urethane) and linear polystyrene formed simultaneously in situ by different mechanisms (radical polymerization and polyaddition) at various initial mixture compositions and initiator and catalyst concentrations have been studied by DSC and light scattering. It has been shown that formation of the poly(urethane)-polystyrene blend is characterized by the same kinetic and thermodynamic features as the previously studied poly(urethane)-poly(methyl methacrylate) system. However, the poly(urethane)-polystyrene blend forms much slower than the poly(urethane)-poly(methyl methacrylate) blend owing to different reactivities of the starting components, which are determined by their chemical nature. Phase separation in the poly(urethane)-polystyrene system, which at initial stages proceeds via the spinodal mechanism, occurs much faster than that in the poly(urethane)-poly(methyl methacrylate) system because of a poor mutual solubility of the poly(urethane) and polystyrene being formed and probably because of a higher mobility of their macromolecules at the onset of phase separation.     

Investigation of infrared calibration methods for application to the study of methyl methacrylate polymerization

Infrared spectroscopy has been used to monitor the polymerization of methyl methacrylate. Concentrations of methyl methacrylate in the reaction mixture were determined by use of three calibration methods. Classical quantitative analysis was used to measure the height of the stretching vibration bands of the vinyl group at 1639 cm(-1). A calibration procedure using the considerably higher intensity of the C = O stretching vibration band of the carbonyl ester group at 1725 cm(-1) seemed useful only for high concentrations of methyl methacrylate, i.e. at the beginning of reaction, because this band overlaps that of poly(methyl methacrylate). Use of second-derivative spectra and measuring their values at 1725 cm(-1) enabled estimation of ten times lower concentrations of methyl methacrylate the calibration using the band from the vinyl group.     

Investigation of infrared calibration methods for application to the study of methyl methacrylate polymerization

Infrared spectroscopy has been used to monitor the polymerization of methyl methacrylate. Concentrations of methyl methacrylate in the reaction mixture were determined by use of three calibration methods. Classical quantitative analysis was used to measure the height of the stretching vibration bands of the vinyl group at 1639 cm^–1. A calibration procedure using the considerably higher intensity of the C = O stretching vibration band of the carbonyl ester group at 1725 cm^–1 seemed useful only for high concentrations of methyl methacrylate, i.e. at the beginning of reaction, because this band overlaps that of poly(methyl methacrylate). Use of second-derivative spectra and measuring their values at 1725 cm^–1 enabled estimation of ten times lower concentrations of methyl methacrylate the calibration using the band from the vinyl group.     

Thermal properties of poly(methyl methacrylate) prepared by emulsifier-free emulsion polymerization

Emulsifier-free emulsion polymerization of methyl methacrylate in the presence of potassium persulfate initiator, taken in several different concentrations, at various pH values was studied with the aim to obtain colloidal crystals. The thermal properties of poly(methyl methacrylate) prepared by emulsifier-free emulsion polymerization, as the starting material for fabrication of photonic crystals, were examined in relation to the synthesis conditions.     

Dynamic behavior of ultrahigh molecular weight poly(methyl methacrylate) in semidilute solutions

The paper presents some rheological investigations on ultrahigh molecular weight (u.h.m.w.) (M_w > 10⁷) poly(methyl methacrylate) in semidilute solutions. The main interest was to study the viscoelastic behavior of the semidilute solutions at different concentrations and temperatures. In the 60‐600 rad/s frequency range, the experimental data show a predominantly elastic response (G′ > G″) for the long poly(methyl methacrylate) chains in toluene.     

Structure and properties of cellulose graft copolymers. III. Cellulose–methyl methacrylate graft copolymers synthesized by the ceric ion method

The ceric ion-initiated graft copolymerization of methyl methacrylate onto wood cellulose was found to depend on the concentrations of initiator, monomer, and cellulose. The structure of cellulose—methyl methacrylate graft copolymers was studied by hydrolyzing away the cellulose backbone to isolate the grafted poly(methyl methacrylate) branches. The molecular weights and molecular weight distributions of the grafted poly(methyl methacrylate) were determined by using gel-permeation chromatography. The number-average (M?_n) molecular weights ranged from 36 000 to 160 000 and the polydispersity ratios (M?_w/M?_n) varied from 4.0 to 7.0. The grafting frequency or the number of poly(methyl methacrylate) branches per cellulose chain calculated from the per cent grafting and molecular weight data varied from 0.38 to 3.2. The structure of cellulose—methyl methacrylate graft copolymers and the effect of stepwise addition of initiator on the structure are discussed.     

Synthesis,surface accumulation,and micellar properties of amphiphilic block copolymers

Amphiphilic block copolymers, i.e., poly(methyl methacrylate)-b-poly(2-dimethylethylammoniumethyl methacrylate), were synthesized by the reaction between two prepolymers. Carboxyl-terminated poly(methyl methacrylate) and hydroxyl-terminated poly(2-dimethylaminoethyl methacrylate) were prepared by radical polymerization of the corresponding monomers in the presence of thioglycolic acid and 2-mercaptoethanol as a chain transfer agent, respectively. Two condensation methods, i.e., DCC and the acid chloride method, were used for the reactions of these prepolymers. The subsequent quarternization produced the amphiphilic block copolymers. Surface property of poly(methyl methacrylate) films containing this amphiphilic block copolymer was examined by measuring contact angles for water. The addition of only 0.5 wt% of the block copolymer was sufficient to make poly(methyl methacrylate) surfaces hydrophilic. The block copolymer formed a polymeric micelle in acetone–water mixed solvent.     

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.     

Identification of a stereoblock poly(methyl methacrylate) sample with a stereocomplex

Acid hydrolysis of a stereoblock poly(methyl methacrylate) sample leads to a mixture of isotactic and syndiotactic poly(methacrylic acid) which can be separated by electrophoresis. The experiment confirms the stereochemical identity between the so-called “stereoblock” poly(methyl methacrylate) and the stereocomplex which syndiotactic and isotactic poly(methyl methacrylate) form in the ratio 2:1. A possible mechanism of replica polymerization is suggested to account for this effect.     

Ultrasonic Modification of Polymers. II. Degradation of Polystyrene,Substituted Polystyrene,and Poly(n-vinyl Carbazole) in the Presence of Flexible Chain Polymers

Abstract

Ultrasonic (20 kHz, 70 W) solution degradations of polystyrene, substituted polystyrenes, and poly(n-vinyl carbazole) have been carried in toluene and tetrahydrofuran at 27 and -20°C in the presence of flexible chain polymers. Polystyrene formed block copolymers at 27°C with stiff-chain polymer PVCz; however, in the presence of flexible chain polymers, e.g., poly(vinyl methyl ketone) or poly(vinyl methyl ether), there were no block copolymers formed. Poly(n-vinyl carbazole) does not seem to form any block copolymers at 27°C with flexible chain polymers, e.g., poly(octadecyl methacrylate) and poly(ethyl methacrylate). Poly(p-chlorostyrene) and poly(p-methoxystyrene) also do not form block copolymers at 27°C with poly(octadecyl methacrylate) but do so with poly(hexadecyl methacrylate). It is quite possible that these may only be blends of two homopolymers. Poly(octa-decyl methacrylate) does yield a block copolymer when sonicated at -15°C with poly(p-isopropyl α-methylstyrene).     

An analysis of the crystallization behavior of poly(ethylene oxide)/poly(methyl methacrylate) blends by spectroscopic and calorimetric techniques

Infrared spectra in conjunction with calorimetric measurements have been used to follow the crystallization process and microstructural changes of poly(ethylene oxide) (PEO) in poly(ethylene oxide) and poly(methyl methacrylate) (PMMA) blends. We have given particular attention to compositions containing low PEO concentrations. The crystallization behavior and the resultant microstructures of PEO are strongly perturbed by the presence of PMMA. In addition, we found phase separation and trans sequences of PEO to be present, especially at low PEO concentrations.     

Thermal degradation of bromine-containing polymers: Part 11—Blends of poly(2,3-dibromopropyl methacrylate) and poly(2,3-dibromopropyl acrylate) with poly(methyl methacrylate) and poly(methyl acrylate)

The products of degradation of blends of poly(2,3-dibromopropyl methacrylate) and poly(2,3-dibromopropyl acrylate) with poly(methyl methacrylate) and poly(methyl acrylate) are predominantly those to be expected from the degradation of the individual polymers. However, the appearance of methyl bromide and methanol from all four blends indicates that some interaction does occur across the phase boundary between the two constituent polymers. This is presumed to consist of the reaction of hydrogen bromide, formed by decomposition of the brominated polymers with the methyl groups of the acrylate and methacrylate polymers.     

Investigation of the detection limit for the determination,by pyrolysis-capillary GC,of the thickness of ultra thin PMMA layers coated on to PET film

The determination of nanometer thick layers of poly(methyl methacrylate) coated on to the surface of poly(ethylene terephthalate) film has been investigated by high resolution pyrolysis gas chromatography without sample pretreatment or modification of the instrumentation used. A good linear relationship was observed between the quantity of the characteristic pyrolysate and the thickness of the poly(methyl methacrylate) layer; the detection limit was sufficient to enable the quantitation of poly(methyl methacrylate)-to-poly(ethylene terephthalate) film thickness ratios of 1:20000 in composite materials.     

Polymerization of adsorbed monolayers. III. Preliminary structure studies in dilute solution of the insertion polymers

Insertion poly(methyl acrylate) and poly(methyl methacrylate) were prepared from monomers adsorbed in monolayers on the surface of montmorillonite clay, both in the presence and in the absence of bifunctional crosslinkers (ethylene glycol dimethacrylate and tetramethylene glycol dimethacrylate). The insertion poly(methyl acrylate) and the crosslinked insertion poly(methyl methacrylate) and dilute-solution properties quite different from conventional polymers of these monomers, the differences including high light-scattering molecular weights combined with low viscosities, low values of the second virial coefficient, unusually large variations of the Huggins' constant k′ with the time-temperature history of the solutions, and low sedimentation velocities. These properties suggest that the insertion polymers have compact structures and are consistent with the postulate of sheetlike macromolecules. The dilute-solution properties of insertion poly(methyl methacrylate) made without crosslinker, unlike those of similarly prepared poly(methyl acrylate), were similar to those of conventional poly(methyl methacrylate). This difference in behavior is attributed to the different tendencies of the two monomers to undergo branching or crosslinking during radical polymerization.     

THE COMPATIBILITY OF BLENDS OF POLY(VINYL CHLORIDE) OR CHLORINATED POLY(VINYL CHLORIDE) WITH POLY(METHYL METHACRYLATE)

IR spectral shifts of carbonyl vibrational absorption for ethyl acetate, which acts analogically as the structural unit of poly(methyl methacrylate), in cyclohexane, chloroform, chlorinated paraffins, poly(vinyl chloride) and chlorinated poly(vinyl chloride) were measured. The results suggest that there are specific interactions between the carbonyl groups and the chlorinated hydrocarbons which could be responsible for the apparent compatibility of poly(vinyl chloride)—poly(methyl methacrylate) and chlorinated poly(vinyl chloride)—poly(methyl methacrylate) blends. Additionally, the effects of the preparation mode of blend films on phase separation and observed compatibility are discussed.     

Phase transitions in solutions of polystyrene with poly(methyl methacrylate) and polybutadiene under deformation

By the cloud point and static sorption methods, phase diagrams are constructed and the concentration and temperature dependences of the Gibbs free energy of mixing and the interaction parameter are determined under static conditions and in a shear field for the poly(methyl methacrylate)-polystyrene-ethyl acetate, polystyrene-polybutadiene-toluene, polystyrene-polybutadiene, poly(methyl methacrylate)-polystyrene, poly(methyl methacrylate)-ethyl acetate, and polystyrene-ethyl acetate systems. Phase separation in the systems both under heating and cooling, as well as coexistence of three phases, is observed in the polystyrene-poly(methyl methacrylate)-ethyl acetate system. Deformation changes the phase separation temperature by 30–40 K.     

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.     

Branching of anionic poly(methyl methacrylate)

A viscometric determination of the degree of branching γ, of poly(methyl methacrylate) obtained by anionic polymerization proved the reaction of the growing center of poly(methyl methacrylate) with the ester group of another polymer molecule, accompanied by the formation of a trifunctional branch point. This reaction occurs if the solution polymerization of methyl methacrylate is initiated: (1) with butyllithium at ?78°C only on attaining 100% conversion and after a long time or at +20°C immediately after the polymerization has set in; (2) with lithium tert-butoxide at +20°C after a long time. The degree of branching of poly(methyl methacrylates) obtained under similar conditions in the presence of tetrahydrofuran reaches higher values than for polymers prepared in toluene. The tacticity of polymers does not affect the experimentally determined γ values.