Cellulose sols have been prepared from native and mercerized wood cellulose, and from viscose rayon by peptization with distilled water after hydrolytic depolymerization. The sols contain cellulose micelles as primary particles, free or in aggregates, resolvable on electron micrographs. The micelles are bundles of 100-150 cellulose molecules. Their width is about 70 A and their length corresponds to the chain length calculated from the degree of polymerization. The micelle dimensions agree with those earlier calculated from the widening of the X-ray reflexions. The micelles contain the same lattice structure as the original cellulose fibres (Cellulose I or 11). The cellulose sols are coagulated by small amounts of electrolyte (0-2-0-3 mmole NaCl or 0.015-0.020 mmole La(N0,) , per litre), and are therefore classed as hydrophobic. Sols from rayon are less sensitive to electrolyte than the others a t high pH values. It is possible to stabilize the sols against coagulation with sodium hydroxide by adding watersoluble wood polyoses (y-cellulose). The stabilization effect is more pronounced for native and mercerized cellulose than tor rayon cellulose sols. So far i t has not been possible to disintegrate the aggregates completely into free micelles.

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SYNOPSISA bulk surface photografting process which is conducted in the interface between two polymer films was designed and investigated. The bulk surface photografting is a highly efficient process. With this method, the surface of hydrophobic polymers can be made hydrophilic in less than 2 s and a grafted layer 5 I m thick can be obtained in 30 s. The kinetic investigation shows that the bulk surface photografting polymerization involves a four-step reaction process: induction period, surface initiation, successive polymerization, and solid-phase crosslinking. The photoreduction of benzophenone (BP) takes place in the interlayer between the LDPE films and is a three-stage process: surface photoreduction, secondary photoreduction, and solid-state photoreduction. With regard to the photoreduction of the initiator caused by hydrogen abstraction, the kinetic studies show that the photoreduction rate has a first-order dependence on the B P concentration. The activation energy of the hydrogen abstraction reaction is about 28.5 kJ (6.8 kcal)/mol. With regard to the photografting polymerization reaction, the reaction order of the rate Rp with respect to the monomer is unity and 0.89 with respect to BP. This means that the termination reaction takes place mainly by combination of polymer chain free radicals and semipinacol free radicals from BP. The activation energy of the overall polymerization reaction is around 8.8 kJ (2.1 kcal)/mol.

A new mechanism has been proposed for the photooxidation of polystyrene as film and in benzene. The initial stage of the photooxidative degradation may involve reactions of singlet oxygen with polystyrene molecules. Singlet oxygen may be formed in the reaction between excited benzene ring in polystyrene molecule and molecular oxygen. The addition of singlet oxygen quenchers such as 1,3‐cyclohexadiene or β‐carotene reduces the rate of polymer degradation in benzene solution. The mechanisms of the photolysis of polystyrene as film and in benzene solution, in vacuo and in the presence of oxygen, are discussed and interpretations proposed. The pronounced yellowing of polystyrene during the photooxidation process is interpreted as a reaction involving benzene ring‐opening photooxidation in polystyrene molecule. These results were obtained by comparing ultraviolet and infrared spectra in experiments of photooxidation of pure liquid benzene and polystyrene film.

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