Cellulose acetate graft copolymer

Fig. 5. Intrinsic viscosity of a cellulose acetate graft copolymer (44.1% combined polystyrene) and the corresponding homopoly-mers in toluene-acetone mixtures...

Preparation of Cellulose-Polystyrene Graft Copolymers. The polystyr-yl mono- and di-carbanions were prepared in THF at -78 °C by using n-butyl lithium and sodium naphthalene as the initiators, respectively. The carban-ions were reacted with dry carbon dioxide. The products were precipitated in methanol, filtered, washed with water and methanol, and dried. Size exclusion chromatography (SEC) established that the molecular weight of the polystyryl monocarboxylate was 6,200 and that of the polystyryl di-carboxylate 10,2000. The mono- and di-carboxylates were reacted with mesylated cellulose acetate in dimethylformamide at 75 °C for 20 h to give the cellulose-polystyrene graft copolymer (GP 1) and crosslinked cellulose-polystyrene graft copolymer (GP 2), respectively. 

Emulsion polymerizations of vinyl acetate in the presence of ethylene oxide- or propylene oxide-based surfactants and protective coUoids also are characterized by the formation of graft copolymers of vinyl acetate on these materials. This was also observed in mixed systems of hydroxyethyl cellulose and nonylphenol ethoxylates. The oxyethylene chain groups supply the specific site of transfer (111). The concentration of insoluble (grafted) polymer decreases with increase in surfactant ratio, and (max) is observed at an ethoxylation degree of 8 (112). 

Poly(vinyl chloride) (PVC) wall covering Cellulose acetate sheet and rods Graft copolymers Nylon (Carothers DuPont)... 

Deters (14) vibromilled a blend of cellulose and cellulose triacetate. The acetic acid content of cellulose acetate decreased with grinding time (40 h) while that of the cellulose increased, suggesting the formation of a block or graft copolymer or of an esterification reaction by acetic acid developed by mechanical reaction. Baramboim (/5) dissolved separately in CO polystyrene, poly(methyl methacrylate), and poly(vinyl acetate). After mixing equal volumes of solutions of equivalent polymer concentration, the solvent was evaporated at 50° C under vacuum and the resultant product ball-milled. The examination of the ball-milled products showed the formation of free radicals which copolymerized. 

The existence of a true graft copolymer was concluded from the weight increase not extractable by polystyrene solvents and by the eventual leveling off of the weight increase while homopolymerization continued. Moreover, the graft of cellulose acetate and styrene after dissolution and precipitation with various solvents and precipitants still showed the infrared absorption of both substituents. In addition to this, the results fitted well with the kinetic theoiy of grafting proved on other systems. 

The properties of cellulosic graft copolymers have been studied to a considerable extent but mainly in the form of grafted fibers or films of ill-defined composition. However, a few properties have been measured on well defined grafts (147). It was found that solutions of cellulose acetate-polystyrene grafts in dimethyl formamide are less tolerant to the addition of polystyrene than cellulose acetate itself. This result was attributed to the greater coil expansion in the case of the graft copolymer. On the other hand, the tolerance of the grafts to each homo-... 

Weldons, J. D., and V. Stannett Some properties of isolated graft copolymers of cellulose acetate and styrene. Polymer preprint A.C.S. Meeting, Detroit, Michigan April 1965. 

In order to make the separation of unreacted cellulose from the apparent graft easier it was acetylated under nondegradative conditions in acetic anhydride-pyridine mixtures. The apparent graft copolymer was first soaked in methanol, methanol was replaced by water and then acetylated with a 1 2 acetic anhydride-pyridine mixture for 36 hr at 100 °C. After the reaction, the product was precipitated with n-hexane. The precipitate was redissolved in chloroform-methanol and reprecipitated with methanol. The reprecipitation was repeated and finally a purified acetylated product was obtained. When pure cellulose was used for the acetylation it was confirmed that by this procedure cellulose is converted almost totally (98.5 to 99,6%) to triacetate. 

The acetylated true graft copolymer was dissolved in methylene chloride, acetone was added to the solution to obtain a 1 1 methylene chloride-acetone composition of the solvent, concentrated hydrochloric acid was added to obtain a 3N solution, and hydrolysis was carried out for 72 hr at 60 °C. The hydrolysis proceeded not in a homogeneous but in a highly swollen state. The branch was precipitated by pouring the hydrolysis mixture into methanol. A part of the precipitated branch was dissolved in m-cresol and filtered. The other part was treated with 1 2 acetic anhydride-pyridine mixture for 15 hr at 100 °C to acetylate cellulose fragments at the end of polystyrene brandies. 

Several graft copolymers were prepared based on the anionic polymerization method to overcome some of the major problems encountered in radical-initiated grafting. This method is used to prepare a living synthetic polymer with mono- or dicarbanions to react with modified cellulosic substrates under homogeneous conditions. For example, polyacrylonitrile carbanion was prepared to react with cellulose acetate to generate a cellulose acetate-polyacrylonitrile graft polymer [142]. 

Similar polymer compatibilization effects were observed by Wellons and co-workers (19) on radiation graft copolymers of cellulose acetate and polystyrene and by Riess and his colleagues (20) on various block copolymers. Hughes and Brown (21) also reported some evidence of compatibilization in a... 

As already intimated, graft copolymers may be prepared without involvement of free-radical initiation. Graft copolymers of nylon-6,6 on cellulose acetate, such as 30, may be obtained by successive, alternate. 

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