Effect of boric acid treatment on the crystallinity and drawability of poly(vinyl alcohol)–iodine complex films

Molecular iodine/polymer complexes

“…Shin et al [168][169][170][171] and Woo et al [172] embarked on the study of the structure and processability of iodina tion products of oriented and unoriented PVA using I 2 /KI solution at room temperature for 24 h. The crystallinity of oriented and unoriented PVA subjected to iodination was 21.3% and 37.0%, respectively. The weight gains and molar ratios of the unoriented and oriented films increased rapidly with I 2 /KI concentration to 1.0 mol/l and 0.5 mol/l, respectively.…”

“…Boric acid seemed to disfavor the crystallization, inducing the formation of an amorphous region [173]. In fact, Woo et al [172] worked on the effect of boric acid on the crystallinity and the drawability of the I 2 PVA films made by iodinating the PVA solution before and after casting its solution, BC and AC, respectively. No change in the crystallinity for the films AC was found, because boric acid could not permeate into the crystal region in the PVA film prior to the boric acid treatment, and the crystallization of the films BC was pre vented, as boric acid may form intramolecular crosslinks on the PVA chain to accelerate the formation of the PVA iodine complex evenly in the solution state.…”

Enhanced oxygen-barrier and water-resistance properties of poly(vinyl alcohol) blended with poly(acrylic acid) for packaging applications

“…At low PAA contents (1% and 5%) the T g values decrease, but they increase significantly at high PAA levels. These results indicate that the intermolecular bond in the hydrogen bonding of PVA chains disturbed the interaction between PVA and PAA at low amounts of PAA, while the effect of steric hindrance reduced the chain mobility leading to higher T g values at the high contents of 10% and 20% . Generally, the T g represents the amorphous regions of a polymer, as well as polymer chain mobility .…”

“…The network structure formed between PVA and PAA will prevent the formation of crystalline regions in the PVA matrix, leading to a decrease in the degree of crystallinity in the PVA . Meanwhile, the crosslinking will induce new quasi‐crystalline phases and a relatively compact structure in the blend films, apparently represented by the decreased intermolecular distance.…”

“…These results indicate that the intermolecular bond in the hydrogen bonding of PVA chains disturbed the interaction between PVA and PAA at low amounts of PAA, while the effect of steric hindrance reduced the chain mobility leading to higher T g values at the high contents of 10% and 20%. 27,28 Generally, the T g represents the amorphous regions of a polymer, as well as polymer chain mobility. 5 In this case, the PAA is crosslinked with PVA in its amorphous regions through chemical condensation, restricting the molecular chain mobility.…”