The mechanism of heterogeneous graft polymerization of vinyl monomers on artificial and biological fibres

Abstract

The matrices chosen for grafting were fibres of diacetylcellulose (DAC) (diameter of monofilaments 30 p) and natural silk. The preparation of the grafted samples and removal of the homopolymers were exactly as described in reference [1] except that methanol was not used in grafting of styrene and methyl methacrylate (MMA) to the acetate fibre. The grafted chains of polystyrene (1)S) and polymethylmethacrylate (PMMA) were removed from the graft copolymers based on DAC by acetolysis of the DAC [2], and PS from the modified natural silk by hydrolysis of the silk with cone. HC1 at 110 ° for 24 hr. I t has been sho~al in both instances that degradat ion of the grafted chains does not occur [1, 2]. The MWD curves of the PS and PMMA isolated in this way were constructed from sedimentation rate diagrams of solutions of PS in methyl ethyl ketone and PMMA in acetone at 20 °, in a Spinco analytical ultracentrifuge. The sedimentation diagrams were treated by the standard method [3]. I t is noteworthy that the thus calculated values of ks, the coefficients of the coneentratior~ dependence for theoretical fractions of the given samples, lie within the limits of the values of k8 found for real fractions of PS and PMMA [4, 5]. This shows that the hydrodynamic bebaviour of the samples isolated from the graft copolymers by breakdown of the original matrices, does not differ from the corresponding behaviour of pure PS and I)MMA, i.e. free from fragments of the mare chain of the graft copolymer. These fragments were not however detected in the infrared spectra. The q-average molecular weights, Mn and Mw were calculated from the MWD curves. The weight-average molecular weight was also measured by light-scattering in a solution of PS in benzene and PMMA in acetone, in a Soficu photogoniodiffusometer. Satisfactory agreement was obtained between the values of Mw calculated from the experimental MWD curves and measured directly by light scattering. In the graphs and everywhere subsequently