Graft Copolymers Of Polystyrene Research Articles

The preparation of graft copolymers of polystyrene with poly‐2‐vinylpyridine

AbstractGraft copolymers have been prepared with polystyrene backbones and poly‐2‐vinylpyridine side chains. The approach used was to couple together two preformed polymers which were themselves separately characterized. Thus, a knowledge of the overall composition and separate descriptions of the two homopolymers gave reasonably well defined grafts. The living‐polymer technique of Szwarc was found to be well suited to this approach. Polystyrene backbones were prepared by anionic polymerization, with Mw/Mn values of less than 1.1 and then chloromethylated to provide reactive grafting sites. The poly‐2‐vinylpyridine side chains were also prepared by anionic polymerization and, while still active, were allowed to react with the chloromethylated polystyrene. The homopolymers were removed by solvent extractions, leaving the graft copolymer as a residue. The molecular weight of the graft was then determined by osmotic‐pressure measurements. Several features of the synthesis and characterization of the grafts and of the homopolymers are discussed. Within very broad limits this method permitted an unrestricted choice of backbone and of side‐chain length and of the average number of side chains per backbone.

Graft copolymers of rubbers and polystyrene prepared with “living” polymers

Graft copolymers of rubbers and polystyrene prepared with “living” polymers

Preparation and characterization of some cellulose graft copolymers. Part IV. Some properties of isolated cellulose acetate–styrene graft copolymers

AbstractA series of purified graft copolymers of cellulose acetate and polystyrene, which were prepared and characterized during the course of an earlier investigation, have been used for some initial property studies. Grafts with high molecular weight backbones and low molecular weight side chains and vice versa, and with both side chains and backbones of high and low molecular weights, were prepared. The graft polymers were found to be insoluble in most solvents but soluble in dimethylformamide and pyridine and in mixtures of solvents for each component. Films cast from mixtures of the grafts and homopolymers showed that the grafts were compatible with the homopolymer of the component with a higher molecular weight. A graft copolymer with high molecular weight backbone and side chains was found to be compatible with both homopolymers separately and with a mixture of both across a wide range of compositions. A blend of the high and low molecular weight grafts was also found to be highly compatible with both homopolymers. The permeability, diffusion, and sorption of gases and water vapor in the grafts and in the corresponding homopolymers was also studied. In the case of water vapor, the sorption in cellulose acetate was much higher than in polystyrene whereas the diffusion was much lower. It was found that the graft polymers showed both diffusion and solution behavior closer to that of cellulose acetate, whereas the permeability constants were more intermediate between those of the two homopolymers. The gas permeability and diffusion constants were found to be intermediate between the values obtained with the two homopolymers.

Density gradient centrifugation of a graft copolymer

AbstractA well‐defined graft copolymer of polystyrene and cellulose acetate has been investigated using the density gradient ultracentrifugation method. The initial sample showed two peaks. These were found to be pure graft copolymer and polystyrene; the latter was easily removed by further extraction of the mixture with benzene. The composition of the graft copolymer was determined from the buoyant densities of the graft and the two homopolymers and found to be 49% polystyrene, 51% cellulose acetate compared with 44.1 and 55.9%, respectively, estimated from the weight loss after acid hydrolysis.

Ordering processes in a system containing an isotactic-atactic polystyrene graft copolymer

THE elucidation in recent times of the basic interelationships of certain properties of graft copolymers [1] sets before investigators the task of making a detailed s tudy of the structure of such systems. One of the interesting problems in this field is the s tudy of the effect of chemical grafting on the ability of a polymer to crystallize when the corresponding homopolymer is a stereoregular, crystalline system. The scanty data in the literature on X-ray diffraction studies of graft copolymers, consisting of ordered and disordered components [2-7], indicate that if the main chain of the eopolymer is capable of crystallization and the side chains are composed of irregular macromolecules or vice versa, according to the X-ray diffraction data such copolymers can preserve their structural order even when there is a considerable content of the amorphous components. This is true, for example, of graft copo]ymers of amylose and methyl methacrylate [2], of hydroxyethylated nylon [5] and in certain other cases [1]. Let us examine the possible explanations of this phenomenon. First, in the case where grafting takes place under heterogeneous conditions on the surface of a crystalline polymer present in the system in the form of fine particles, fibres or films, which do not pass into solution when the graft copolymer is formed, it may be concluded from X-ray diffraction data that surface grafting of this type preserves the structural pat tern characteristic of the crystalline polymer itselL This type of grafting, taking place on the surface of crystalline aggregates of the first component should easily be achieved by the radiation and mechanochemical methods of preparation of graft copolymers, in which a polymer swollen with another monomer is used, and also by the method involving ozonization

The synthesis and properties of isotactic-atactic polystyrene graft copolymers

RECENT studies of the properties of graft copolymers has enabled certain general characteristics of this class of polymers to be explained.We have shown previously [1-5] on the example of graft eopolymers of the amphipathic type that their structural and thermomechanical properties are a distinctive combination of the properties of the two components. At the same time the solubility of these eopolymers is considerably reduced and this is explained by the mutual screening effect of the components [3, 6]. In our work in this field the graft eopolymers studied were obtained from components differing widely both in chemical nature and physical properties (for example polystyrene-polyacrylic acid and polystyrenepolyvinylalcohol grafts, etc. [1-6] and moreover in these systems one of the polymeric components was a polymer with a rigid chain and a glass temperature (Tg) above its decomposition temperature. Furthermore both homopolymers were non-crystalline systems of irregular structure [3-6]. I t was of interest to s tudy the properties of a graft copolymer consisting of chains of the same chemical nature but possessing different structures. Copolymers of crystalline, isotactie (main chain) and amorphous, atactic (side chains) polystyrene were chosen for the present work. I t is known that in ordinary, atactic polystyrene the high-elastic state is covered by a temperature interval of 50 ° (Tg90°; T m 140°). For crystallized, isotactic polystyrene, with the same chemical structure but a different spatial arrangement of the asymmetric carbon atoms in the backbone (dd or ll) the total absence of the high-elastic state is characteristic, but on the other hand the melting point (230 ° ) is high. On conversion to the amorphous state, when heated above its T~ (90°), this polymer again acquires the properties of a rigid plastic [7]. On grafting on to crystalline, isotactic polystyrene ataetic polystyrene chains, with their characteristic random sequence of asymmetric carbon atoms, the production of a graft copolymer with a well defined high-elastic region while maintaining a high melting point would be expected [5]. Such a graft copolymer would also provide a suitable model for the s tudy of the structural properties

Initiation of graft polymerization on cellulose by hydroxyl radicals and by ceric salts

Landells and Whewell have previously reported that vinyl monomers are polymerized “within viscose filaments” by hydrogen peroxide in the presence of ferrous salts and the polymers are not extractable. Such products, obtained by polymerization of acrylonitrile and styrene in viscose, have now been acetylated. Fractionation of the acetylated products has yielded graft copolymers of polyacrylonitrile and polystyrene, respectively, on cellulose triacetate. It is concluded that hydroxyl radicals initiate graft polymerization of acrylonitrile and styrene on cellulose. A similar approach, utilizing acetylation and fractionation, has been used to demonstrate that Mino and Kaizerman's method of initiation of graft polymerization with ceric salts is applicable to cellulose and results in true graft polymerization.

Synthèse de copolymères greffés par action des rayonnements ionisants sur des solutions de polyisobutylène dans le styrolène

AbstractOn étudie la polymérisation radiochimique du styrolène en présence de polyisobutylène. La polymérisation du styrolène est amorcée par les radicaux provenant du styrokléne et les radicaux provenant du polyisobutyléne, ces deux sortes d'amorcage conduisant respectivement à la formation de polystyroléne et de copolymère greffé, polystyroléne sur polyisobytyléne. On édie l'influence de l'intensité du rayonnement et de la concentration initiale en polyisobutylène sur la cinétique de la réaction.