synopsisExperimental data are presented describing the formation of porosity in styrene-divinylbenzene copolymers as a function of the organic components present during the suspension polymerization. The reaction system contains a mixture of diluents such as toluene and hexane, which results in matrices that differ significantly in pore structure from the porous resins so far known. From these data a model of the physical structure is proposed.

SynopsisThe collapse of pores in styrenedivinylbenzene copolymers and corresponding ion-exchange resins was studied during the removal of solvating liquids. The process can be followed in a most simple way by measuring the volume of the bead-shaped copolymers upon drying. Other parameters observed during drying were the apparent density and incidently the internal surface. The collapse of pores is considered to be a result of cohesional forces when solvated polymer chains are approaching each other by loss of solvent. The effect will thus be more pronounced in gel-type networks than in porous ones. In porous networks, the effect will be stronger in smaller pores than in larger ones. It is shown that crosslinks, increasing the rigidity of the structures, will favor the conservation of porosity. In ion-exchange resins the pore stability is best when the material is in its lowest state of hydration. Generally, the collapse of pores is a reversible process. The collapsed material can in most cases be reswollen by the proper choice of solvent.

SummaryA polyelectrolyte synthesized from cis-1,4-polyisoprene, containing aminosulfonate and carboxylate groups was shown to have an anticoagulant activity of about 1/30 compared with heparin. Because the substance prevents the coagulation of plasma in the presence of thrombin it is assumed that it acts as an antithrombin.Recently, the addition reaction of N-chlorosulfonyl isocyanate and cis-1,4-polyisoprene has been reported.' It was shown that the addition product upon treatment with alkali gave a water soluble polyelectrolyte (A) containing the following structural unit :

A series of copoly(alpha-amino acids) with varying percentages of hydrophilic (L-aspartic acid) and hydrophobic monomers (L-leucine, beta-methyl-L-aspartate, and beta-benzyl-L-aspartate) were implanted subcutaneously in rats and the macroscopic degradation behavior was studied. Three groups of materials (A,B,C) with different ranges of hydrophilicity were distinguished: A) hydrophobic materials showed no degradation after 12 weeks; B) more hydrophilic materials revealed a gradual reduction in size of the samples, but were still present after 12 weeks; and C) hydrophilic copolymers disappeared within 24 hr. The tissue reactions caused by the materials of group A resembled that of silicone rubber, whereas those of group B showed a more cellular reaction.

SUMMARY:The synthesis of poly(y-p-biphenylmethyl-L-glutamate), PBPLG, (poly{ L-imino-1 -[2-(4-biphenylylmethoxycarbonyl)ethyl]-2-oxoethylene}), (Id) is described. The viscosity behavior of this polymer in benzene/dichloroacetic acid mixtures (~= 0 , 2 . 1 0 -~-1,4. g/cm3) at 25°C is investigated. The results are compared with measurements on poly(ybenzyl-L-glutamate), PBLG, (poly [ L-imino-1 -(2-benzyloxycarbonylethyl)-2-oxoethylene]), (lc) under the same conditions. A transition from a rigid hydrogen bonded helix to a random solvated coil occurs in two stages for both: PBPLG (first stage 0-55%, second stage 55-100% dichloroacetic acid) and PBLG (first stage 0-