Graft copolymer Experimental conditions

Several block and graft copolymers have been shown to form stable aggregates under thermodynamically poor solvent conditions, as a result of differences in the solubility of different parts of a macromolecule. Whereas in a good solvent the experimentally measured value of A2 for a copolymer represents the balance of all the multiple interactions, under thermodynamically poor conditions A2 is mainly determined by the interaction of the groups situated on the polymer-solvent interface. Groups which form the hydrophobic core and are not in a contact with the solvent do not contribute significantly to the solution properties of the copolymer. 

Table 4 summarizes the reaction conditions and the experimental results. Overall, the experimental results clearly show a new class of PE graft copolymers which can be conveniently prepared by the tranformation of metallocene catalysis to anionic graft-from polymerization. 

The polymerization reaction in aqueous suspension of vinyl chloride in the presence of an ethylene-propylene saturated elastomer occurs with the formation of poly (vinyl chloride) homopolymer and rubber-poly (vinyl chloride) grafted copolymers. The first grafting reaction proceeds as far as diffusion of the monomer inside the particles in suspension is possible afterwards, some chain branching of grafted PVC is possible. Under our experimental conditions the amount of grafted rubber does not exceed 60% of the initial rubber and is little influenced by the type of initiator used. 

The modification of the properties of fibrous cotton cellulose through free-radical initiated copolymerization reactions with vinyl monomers has been investigated at the Southern Laboratory for a number of years. Both graft and block copolymers are formed. Under some experimental conditions the molecular weight of the polyvinyl polymer, covalently... 

Generally, macromonomers are (co)polymerized by free-radical processes owing to convenient experimental conditions, availability of a large number of comonomers, and insensitivity of most chemical functions to the polymerization conditions. Nevertheless, some macromonomers with a suitable end group have been (co)polymerized by cationic polymerization. Provided that living cationic polymerization conditions are applied, well-defined graft homopolymers or copolymers can be prepared with a predetermined and uniform number of branches. 

Table 3. Experimental conditions of thin-layer chromatography for graft copolymers...

Graft copolymerization reactions of fibrous cellulose with vinyl monomers were initiated at free radical sites formed on the cellulose molecule by interaction with radiation, by reaction with Ce4+ ions in acidic solution, or by H abstraction by OH radicals formed by reaction of Fe2+ ions with H202 in aqueous solution. The effects of experimental conditions on the location of these sites on the cellulose molecule and on the reactions were studied by ESR spectroscopy. The molecular weights of the grafted copolymers and the distribution of the polymers within the fibrous cellu-losic structure were determined. Some of the properties of the copolymers are discussed. 

The morphology of the fibrous cellulose graft copolymers depended on the method of initiation of free radical formation, experimental conditions during the copolymerization, chemical modification of the cellulose before reaction, and the type of monomer used (60). Variations in the shape of the fibrous cross section, in layering effects in the fiber, and in the location and distribution of the grafted copolymer in the fiber were observed by electron microscopy (61). Cotton cellulose—poly (acrylonitrile) copolymer was selected to show the possible variations in location and distribution of the grafted copolymer in the fiber. 

A graft copolymer of collagen (as well as other proteinaceous materials) with methyl methacrylate has been made by polymerization initiated by tri-n-butylborane (31). Kudaba and co-workers also modified collagen by treating it with epichlorohydrin (32, 33) or epoxy resins (34) with BFs Et20 as catalyst. Such treatments could be valuable for improving certain properties of leather, but the experimental conditions preclude their use for clinical applications. 

The experimental conditions for grafting reactions have been reported dse-where together with the methods used for analyzing graft copolymers. 

Ruckenstein and Zhang reported that the anionic copolymerization of 4-(vinylphenyl)-l-butene with styrene in toluene/THF at —40 °C gives well-defined polymers,133 since under these experimental conditions the vinylic double bond is selectively polymerized. The copolymers were subjected to hydrosilylation for the introduction of Si—Cl groups at the olefinic double bonds. These groups were used as grafting sites for the linking of PSLi, PILi, and PMMALi living chains in order to synthesize PS- -... 

Runs 1-4 clearly show that, in the absence of AcCL, even if the CL conversion does not exceed 20%, graft copolymers having up to 32% by weight of polyamide can be obtained. It is interesting that, except for run 4, the polymerized CL was found mostly as grafted polyamide chains and, to a smaller extent, as PA 6 homopolymer. Slightly better results were obtained in the bulk polymerizations with respect to those carried out in the presence of xylene under the same experimental conditions. 

This paper deals with the conditions of an effective stabilization. The miscibility behaviour of blends A/ p and A/B/aP where A and B are homopolymers and ap is a symmetric two-block copolymer of the same monomer units as A respectively B or a graft copolymer was analyzed theoretically by model calculations, and experimentally by electron microscopy and X-ray scattering. Due to the uniformity of the two-block copolymers, ( P(S-b-MMA) ) blends with a high degree of structural control are obtained. The morphology of the blends of one homopoply-mer and one block copolymer depends on the chain length ratio X between the homopolymers and the block copolymer. 

Graft copolymers of pivolactone synthesized by anionic ring-opening by carboxylate ion under mild conditions have been reported. The experimental... 

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