Poly Alkyl Methacrylate Research Articles

Antibody-detectable changes in fibrinogen adsorption affecting platelet activation on polymer surfaces

Reactivity of platelets with an artificial surface exposed to whole blood is correlated with the concentration of adsorbed fibrinogen detectable by antifibrinogen antibodies. To examine the effect on platelets of the organization (distribution, orientation, conformation) of fibrinogen adsorbed on a hydrophobic surface, we studied the binding of polyclonal and monoclonal antifibrinogen antibodies to polyalkyl methacrylate polymers previously exposed to purified fibrinogen solution or diluted plasma and compared the results with platelet retention in methacrylate bead columns. There was an increase in platelet retention following diluted plasma pretreatment, which was eliminated by a polyclonal antibody against fibrinogen or against a gamma-(395-411) peptide from fibrinogen and was reduced by monoclonal antibodies (4A5, 4-2) against other COOH-terminal gamma-chain epitopes. Monoclonal antibody 10E5 against the fibrinogen receptor GpIIb/IIIa totally inhibited platelet retention in the bead columns. Our data suggest that different methacrylate polymers induce different changes in adsorbed fibrinogen, which may interfere with its interaction with platelets, and that platelet retention in a methacrylate bead column involves interaction of the COOH-terminal end of the gamma-chain of adsorbed fibrinogen with platelet GpIIb/IIIa receptors.

On the intramolecular ordering and the mobility mechanism in solutions of comb-like polyalkyl methacrylates

The dipole polarization relaxation method was used to investigate molecular mobility in solutions of polyhexadecylmethacrylate (PMA-16) in toluene. The previously obtained data on molecular mobility in polymers of type PMA- n ( n = 1, 4, 8, 10, 16 and 22) have been analysed. It is shown that a new relaxation process appears as a result of the partial aggregation of side-chains in the case where n > 10.

Influence of polyalkylmethacrylate and sulphurized ester on oil film thickness in an elastohydrodynamic point contact

The aim of this investigation is to determine how additives in a base oil affect the central oil film thickness in an elastohydrodynamic rolling point contact. The experiments have been carried out using a sapphire disc and a steel ball and the film thickness has been measured by means of optical interferometry. A detailed description of the apparatus is given. Two different additives have been used, polyalkylmethacrylate (PMA) and sulphurized ester (SE). Each of them have been mixed in a superrefined naphthenic base oil at five different concentrations. The results show that the central oil film thickness increases with increasing concentration of additive. This is because the additives increase the oil viscosity. If this effect is compensated for, 0.1 wt.% PMA or 0.63–2.5 wt.% SE give the best relative oil film build-up. There is consequently no reason to use more additive in the base oil unless one wants to have a thicker oil film because of the viscosity-increasing effect.

Does the conformation of adsorbed fibrinogen dictate platelet interactions with artificial surfaces?

Platelet activation by polymer surfaces is thought to require preliminary adsorption of fibrinogen and perhaps changes in fibrinogen conformation. We measured fibrinogen adsorption by a series of polymers by two methods, using either 125I-labeled fibrinogen or 125I-labeled antifibrinogen antibodies, and correlated the results with platelet reactivity (retention and secretion) in columns of beads coated with the polymers. For polyalkyl methacrylates with 1 to 4 carbon side chains, platelet reactivity varied directly with increasing length of the alkyl side chain and with the quantity of bound fibrinogen recognizable by antifibrinogen antibody but not with the total quantity of fibrinogen adsorbed. The same pattern of results was seen with five antibody preparations, including affinity-purified Fab fragments against the D or E domain of fibrinogen. Tests of platelet retention and fibrinogen binding to four polyalkyl acrylates and to three unrelated polymers (polystyrene, polymethyl methacrylate, and a polyether polyurethane) indicated that platelet retention correlated positively with both total fibrinogen binding and with the amount of antibody-recognizable fibrinogen bound. Drugs that block platelet aggregation, but not adhesion, did not alter the hierarchy of platelet retention to the polyalkyl methacrylates. These data suggest that, contrary to previous views, platelet adhesion to artificial surfaces increases with increasing surface coverage of adsorbed fibrinogen if the bound fibrinogen maintains a conformation such that its functional domains remain recognizable by antibody probes.

Does the Conformation of Adsorbed Fibrinogen Dictate Platelet Interactions With Artificial Surfaces?

Platelet activation by polymer surfaces is thought to require preliminary adsorption of fibrinogen and perhaps changes in fibrinogen conformation. We measured fibrinogen adsorption by a series of polymers by two methods, using either 125I-labeled fibrinogen or 125I-labeled antifibrinogen antibodies, and correlated the results with platelet reactivity (retention and secretion) in columns of beads coated with the polymers. For polyalkyl methacrylates with 1 to 4 carbon side chains, platelet reactivity varied directly with increasing length of the alkyl side chain and with the quantity of bound fibrinogen recognizable by antifibrinogen antibody but not with the total quantity of fibrinogen adsorbed. The same pattern of results was seen with five antibody preparations, including affinity-purified Fab fragments against the D or E domain of fibrinogen. Tests of platelet retention and fibrinogen binding to four polyalkyl acrylates and to three unrelated polymers (polystyrene, polymethyl methacrylate, and a polyether polyurethane) indicated that platelet retention correlated positively with both total fibrinogen binding and with the amount of antibody-recognizable fibrinogen bound. Drugs that block platelet aggregation, but not adhesion, did not alter the hierarchy of platelet retention to the polyalkyl methacrylates. These data suggest that, contrary to previous views, platelet adhesion to artificial surfaces increases with increasing surface coverage of adsorbed fibrinogen if the bound fibrinogen maintains a conformation such that its functional domains remain recognizable by antibody probes.

Synthesis of V. I. improvers by copolymerization of decyl methacrylate with styrene

This article demonstrates how copolymerization can be used to improve the quality of polyalkyl methacrylates. Benzoyl peroxide was used as an initiator for copolymerization performed in toluene solution. The influences of the concentrations of initiator and monomer mixture in toluene, the temperature, the length of the reaction period, and the quantity of styrene were investigated. The results indicate that as the reaction temperature was raised from 70/sup 0/ to 90/sup 0/C, the molecular weight of the copolymer decreased from 20,000 to 12,000 and the yield remained unchanged. An increase in the content of styrene from 10% to 40% led to an increase in the molecular weight of the copolymer from 10,000 to 17,000. When the volume ratio of toluene to monomer mixture was increased, the molecular weight of the copolymer decreased while the yield remained constant. It is determined that by varying the quantities of stryene and toluene, the molecular weight of the copolymer can be regulated without changing the temperature or the initiator concentration.

Determination of content of polyalkyl methacrylates in pour-point depressants by means of IR spectroscopy

This article reports on the application of infrared spectroscopy to the determination of the relative quantities of polymer and monomer in a reaction medium. A mixture of alkyl methacrylates were used as the monomer and a mixture of hydrocarbon solvents was used as the reaction medium. The spectra of 11 standard samples with relative concentrations of polymer (calculated for the mixture of polymer with monomer) at 10% intervals in the range 0-100% by weight was used as a basis for constructing a calibration relationship. The samples were prepared by mixing and heating the polymer, monomer, and hydrocarbon solvent, the content of solvent being 50% by weight in all of the artificial blends. It is concluded that the proposed method can be used to determine the quantity of active substance in pour-point depressants for use in various petroleum products with a known content of hydrocarbons solvent used as the medium for the polymerization reaction.

Dielectric and NMR studies of the molecular movements in comb-like polyfluoro-alkyl acrylates and polyfluoro-alkyl methacrylates

The characteristics of the molecular movements have been studied in a series of polyacrylate and polymethacrylate homologues containing fluoro-alkyl fragments in the branches. The ability of the secondary groups to arrange themselves in an orderly fashion and to crystallize has been shown to apply to the lower homologues; the transition to the highly-elastic state and the melting have shifted into higher temperature ranges when compared with those of the polyalkyl acrylates (PAA) and polyalkyl methacrylates (PAMA). Relaxation processes due to the mobilities of the ester and the polar end groups in the branches, the α-methyl groups, and also the fluoromethylene fragments, have been detected at low temperatures. The comb-like homologues in the series with differing compositions have been found to have dipolar polarization relaxation times of the ester groups at low temperatures which depend to a large extent on the interactions and the arrangement of the side chains.

New developments in photochromic polymers and related phenomena

Abstract

Effect of the length of side ester groups of polymethacrylates on the rheological properties of their solutions in hydrated monomers

The rheological properties of concentrated solutions of “comb-like” polyalkylmethacrylates (PMA) were investigated in their hydrated monomers. It is shown that solutions of PMA with up to six carbon atoms in side ester groups have viscous flow anomalies which decrease with increasing length of the side chains and increase with rising molecular weight of the polymers. Solutions of MPA that have six or more carbon atoms in the side groups do not exhibit anomalous viscous flow over the ranges of shear rates and molecular weights examined. The viscosity of the PMA solutions is reduced on increasing the number of carbon atoms in the side ester groups.

Rheological properties of comb-like polyalkylacrylates and polyalkylmethacrylates

A study was made of the viscosities of polyalkylacrylate (PA) and polyalkylmethacrylate (PMA) melts containing 4 to 18 carbon atoms in the side chain. It was shown that with an increase in the length of side branches, viscosity and any anomaly in viscosity in homologous series markedly decreases, the viscosity of polymers with the same side radical being higher for PMA, compared with PA. The activation energy of viscous flow E decreases with an increase in the length of the side radical. The maximum corresponds to the first members of the series—polymethylmethacrylate and polymethylacrylate. The value of E for polymers with long alkyl side radicals is equal to the value of E of polypropylene, in contrast to the poly-α-olefin series, for which E corresponds to E of linear polyethylene for higher homologues. It was found that PA and PMA with long side branches capable of being crystallized may flow at temperatures somewhat lower than melting point. The formation of discontinuities is a typical feature of flow curves in this case. It was shown that the formation of this discontinuity is due to the breakdown of crystalline structure of the polymer.

Ultraviolet irradiation of poly(alkyl acrylates) and poly(alkyl methacrylates)

AbstractAcrylic and methacrylic homopolymers containing different side groups were irradiated with ultraviolet light in the presence of air. The changes of molecular weight distributions of the irradiated polymers were analyzed by means of gel permeation chromatography (GPC), and the rates of chain scission and crosslinking were estimated. As the result of this study, it was found that chain scission takes place more easily in polyalkyl methacrylates than in polyalkyl acrylates.

Thermoelastic behaviour of polyalkyl methacrylates

Thermoelastic behaviour of polyalkyl methacrylates

Study of the polystyryl-lithium reaction with polyalkyl methacrylates and of graft copolymer synthesis of a certain composition and structure

Much attention is given at present to the synthesis of hybrid polymers for the purpose of enlarging the fields of practical uses. The greater interest in the study of graft copolymers is also due to their detection amongst natural high mol. wt. compounds. Of special interest is the aspect of the correlation problem of composition and structure of the graft copolymers with conformations of their macromolecules due to interaction with the grafted chains, the possibility of intramolecular structuration and the degree of orientation, but also with the hydrodynamic properties of the macromolecules. A quantitative correlation of the physical characteristics of graft copolymers with the chemical and stereo-chemical structure of their chains would be feasible only with model polymers in which the composition and structure could be varied within fairly large limits.

Multiple Transitions in Polyalkyl Methacrylates

A series of polyalkyl methacrylates, two hydroxylated methacrylates, polymethoxy ethyl methacrylate, and polymethyl acrylate have been studied by linear expansion and torsion-pendulum measurements, in the temperature range from −180°C to just above the respective glass transition temperatures. The length-temperature data (L-T) were analyzed by a least-squares differentiation procedure, based on moving arcs, to give directly the thermal expansion coefficients as a function of temperature. The L-T measurements suggest the existence of two Tgg transitions (Tg−100<Tgg<Tg) in the polymers with the more flexible side chains, and one transition for polymers with bulky side groups. There is also evidence of a third Tgg transition at about −120° to −90°C, which may be associated with adsorbed water molecules. In similar fashion to that of Tg, the location of the Tgg transitions decreases upon increasing the length of the n-alkyl side chain. The hydroxylated polymers have higher Tg's than the corresponding alkyl samples, and have thermal expansion coefficients only about one-half as large, both features being a result of interchain hydrogen bonds. Torsion-pendulum measurements indicate only one clear-cut Tgg transition region; hence, it seems that the two Tgg transitions observed in the expansion studies cannot be unequivocally resolved by dynamic measurements. Expansion coefficients of the n-alkyl series suggest the retention of some excess free volume below Tg for side chains larger than ethyl. Substitution of 3α′g″, the expansion coefficient below our second Tgg transition, into the Simha-Boyer equation (αl-αg) Tg gives a value close to their empirical constant. This supports their suggestion that polymers with pronounced subgroup motions exist in an iso-free volume state below the subgroup transition temperature.

On a General Relation Involving the Glass Temperature and Coefficients of Expansion of Polymers

Treating the glass temperature TG of polymers as an iso-free volume state allows one to derive the result (αL—αG). TG=K1, a constant; or the approximate result αLTG=K2, another constant. The α's are the coefficients of cubical expansion for 100% amorphous polymer above and below TG. K1 is 0.113 for a wide variety of polymers differing in cohesive energy density, chain stiffness, and geometry. We thus have a general criterion for TG. K2 is 0.164. This latter relation combined with the principle of corresponding states, results in an expression for Tg as a function of cohesive energy density and chain rigidity. The polyalkyl methacrylates which have side-chain transitions below TG follow the first equation if αG is replaced by αG′, the expansion coefficient below the side-chain transition. Polymer-solvent systems are similar to the polyalkylmethacrylates. Two additional products, αL·TM and ΔCP·TG, where TM is the melting point of the polymer and ΔCP is the jump in specific heat at TG, are approximately constant.

Comparison of unperturbed molecular parameters of methacrylate polymers

AbstractPolyalkyl methacrylate polymers were prepared by the emulsion technique and fractionated. The intrinsic viscosity molecular weight relations were established in several ideal solvents. Light scattering determinations were run on polyalkyl methacrylates in an ideal and a nonideal solvent. The results of this experiment have proven that neither size nor shape of the solvent molecules has an effect on the dimensions of the unperturbed polymer. Also, it was shown that the unperturbed polymer dimensions are not altered by the choice of mixed or single theta solvents. It was found that the degree of chain extension increases as the size of the pendant groups (methyl, ethyl, and n‐butyl) increases.

Viscosity characteristics of polyalkyl methacrylate solutions

Viscosity characteristics of polyalkyl methacrylate solutions