Highly isotactic poly(vinyl alcohol) derived from tert-butyl vinyl ether. Part IV. Some physical properties, structure and hydrogen bonding of highly isotactic poly(vinyl alcohol) films

Highly Isotactic Poly(vinyl alcohol) Derived from tert-Butyl Vinyl Ether V. Viscoelastic Behavior of Highly Isotactic Poly(vinyl alcohol) Films

“…The degree of crystallinity of this LI-PVA film, obtained from a DSC measurement (only approximately because of its poor thermal stability at high temperatures 14 ), was c $ 0:3. As seen in Figure 5, the local twisting motion (seen as the a dispersion) and micro-Brownian motion ( a dispersion) of the respective chains in the non-crystalline region are essentially the same in the PVA films of various stereoregularities (mm ¼ 0:14{0:78).…”

“…[10][11][12] We found interesting features of these highly isotactic PVAs (HI-PVAs) being different from those of LI-PVA and ordinary atactic PVA (A-PVA). 10,13,14 In particular, we compared the melting temperature T m , degree of crystallinity c , and 13 C spin-lattice relaxation time T 1C of the crystalline components for PVA samples with different tacticities (including HI-PVA) to find that these physical quantities show clear minima at the mm fraction = 0.4-0.5 when plotted against mm.14 This result suggests that the structural disordering associated with the decrease in the crystallinity occurs most significantly in this mm range. In relation to these minima, FT-IR spectroscopy confirmed the formation of the new crystal form for HIPVAs with mm > 0:55 and solid-state 13 C NMR spectroscopy revealed that all OH groups are allowed to form successive intramolecular hydrogen bonding along the respective chains in the crystalline region for HI-PVAs with mm > 0:7.…”

“…[10][11][12] We found interesting features of these highly isotactic PVAs (HI-PVAs) being different from those of LI-PVA and ordinary atactic PVA (A-PVA). 10,13,14 In particular, we compared the melting temperature T m , degree of crystallinity c , and 13 C spin-lattice relaxation time T 1C of the crystalline components for PVA samples with different tacticities (including HI-PVA) to find that these physical quantities show clear minima at the mm fraction = 0.4-0.5 when plotted against mm.…”

Non-mulberry silk sericin/poly (vinyl alcohol) hydrogel matrices for potential biotechnological applications

“…The first one near 100 • C is due to the loss of water from the structure [40]. The second peak corresponding to the melting temperature T m of PVA was seen near 200 • C. T m of PVA and its various modified forms have been reported to be at 225 • C, at 190 • C, between 150 • C and 220 • C, around 200 • C to 225 • C and at 206.01 • C [36,[41][42][43]. In this study, PVA-F had a melting temperature of 224 • C whereas S0 and S2 showed a melting temperature of 212 • C and 211 • C, respectively.…”

“…These bands are assigned to the CH 2 rocking motion or the skeletal motion and to the stretching of the C-C bond or the skeletal motion of the main chain, respectively [36]. These bands are used for determining the sydiotacticity and isotacticity of polymers [34,36]. Tacticity of a polymer chain refers to the arrangement of pendant groups along the backbone chain of a polymer.…”