Structure–property relationships of poly(vinyl alcohol). I. Influence of polymerization solvents and temperature on the structure and properties of poly(vinyl alcohol) derived from poly(vinyl acetate)

Abstract

SynopsisThe solubility properties of poly(viny1 alcohol) (PVA) vary with the method of preparation of the poly(viny1 acetate) (PVAc) from which it is derived. PVAc was prepared with free-radical catalysts over a range of temperatures from -78 to 90°C. with solvents of varying chain-transfer ability. The corresponding PVA samples varied in their resistance to dissolution in water. Their high-resolution proton nuclear magnetic resonance spectra showed no differences in tacticity. Data on 1,Zdiol content showed only minor differences. Hence, the increase in resistance of PVA to dissolution in water arising from changes in chain-transfer activity of the solvent used in vinyl acetate polymerization is largely attributable to a decrease in molecular weight, and the increase in resistance of PVA to dissolution in water arising from a decrease in the temperature of the vinyl acetate polymerization is largely attributable to a decrease in both long and short branches. Evidently, with polar polymers having small side groups, tacticity is iiot the only factor influencing property variation; that is, variations in stereoregularity influence more the crystallinity of the sample as measured by density or x-ray methods than the ultimate crystallizability under conditions of mechanical and thermal treatment. In this regard polar polymers having small side groiips differ from nonpolar polymers.

Vinyl Alcohol Polymers

“…The reaction is an abstraction of the hydrogen on the acetyl group of the vinyl acetate (187)(188)(189). The growing radical is transferred to the vinyl acetate monomer, which then reinitiates the polymerization.…”

“…The reaction results in an unsaturated end group, which is still polymerizable. The inclusion of this terminal end group in a growing chain leads to a trifunctional branch point with the incorporation of the entire polymer molecule as a long-chain branch (185)(186)(187)(187)(188)(189)(190)(191)(192).…”

Synthesis and Characterization of Complexes of Remodulated Polyvinyl Alcohol Conjugates

“…XRD Spectra of pure PVA and RPVA Figure.8 shows the x-ray diffraction of PVA and RPVA samples at room temperature in the scanning range 6˚ ≤ 2θ ≤ 60 ˚. Spectrum of pure PVA shows an intense reflection peak at 2θ = 19.9˚ diffused in the hallow amorphous region and was assigned to a mixture of (101) and (10ĺ) reflections [18]. The appearance of sharp reflections and diffuse scattering is characteristic of crystalline and amorphous phases of conventional semi-crystalline polymers [19].…”

Influence of K2CrO4Doping on the Structural, Optical and Dielectric Properties of Polyvinyl Alcohol/K2CrO4Composite Films

“…The crystalline nature of PVA results from the presence of strong inter and intramolecular hydrogen bonding between different monomer units of PVA [22] . The crystalline peak at 2θ = 19.4° of PVA can be assigned to (101) reflections [23] . Further, from Figure 6, it is evident that the relative intensity of this peak decreases as the concentration of K 2 CrO 4 increases.…”