Inhibition of Recrystallization of Ice Grains by Adsorption of Poly(Vinyl Alcohol) onto Ice Surfaces

Abstract

The effect of poly(vinyl alcohol) (PVA) on recrystallization of ice was studied by comparison with the effect of antifreeze protein (AFP) type I. Polycrystalline ice wafers consisting of numerous ice grains, whose initial size was less than 130 μm (i.e., less than the thickness of the ice wafer) were made from solutions containing PVA or AFP type I at various concentrations. The ice wafers were annealed between −2.3 and −2.0 °C for 5 h, and then the size of the ice grains was measured using digital microscopy. Even at a PVA concentration as low as about 5 × 10-7 mol/L, the size of the annealed ice grains made from the PVA solution did not change significantly from the initial size, indicating that PVA is as effective as AFP type I in inhibiting ice recrystallization. The effectiveness of PVA increased (i.e., the grain size decreased) with increasing molar concentration, molecular weight, or degree of hydrolysis of PVA. The function of PVA molecules in the inhibition of recrystallization was analyzed by using the Langmuir adsorption equation.

Poly(vinyl alcohol) Scaffolds with Tailored Morphologies for Drug Delivery and Controlled Release

“…In particular, it has been reported that PVA can retard ice crystallization; the effectiveness of PVA not only depends on the PVA content in the water but also on its molecular weight and degree of hydrolysis. [20] Given that the ice crystal size formed during the ISISA processing of the aqueous PVA solutions ultimately determines the macroporous structure of the resulting PVA scaffolds, we will focus on the study of three main variables in this work; the PVA content, the molecular weight of the PVA, and the freezing rate. Note that, in the present work, the degree of hydrolysis is similar for every PVA (see Experimental) and, hence, will not be a variable under study.…”

“…Recent work on the inhibition of recrystallization of ice grains by the presence of PVA reveals that the effectiveness in inhibiting ice crystal formation increases with the molecular weight of the PVA. [20] The ability for ice-crystal growth in the presence of any solute depends on the adsorption and desorption balance of such a solute on the surface of the ice crystal. Irreversible adsorption would completely stop icecrystal growth while full desorption would allow for free crystal growth so that one can assume that adsorption onto ice is a dynamic equilibrium.…”

Ice Recrystallization Inhibition and Molecular Recognition of Ice Faces by Poly(vinyl alcohol)

“…Up to now, only very few synthetic polymers have been reported that show ice recrystallization inhibition by adsorbing to ice crystals, for example poly(vinyl alcohol) (PVA) or double hydrophilic block copolymers. [14][15][16][17] However, their mechanism of action is as yet unknown. [14,18] Herein, we present experiments in which we quantify the effect of PVA on ice recrystallization and propose an adsorption mechanism that can explain the observed effects.…”

“…In addition, we study a nonadsorbing water-soluble polymer, poly(ethylene glycol) (PEG10; M w = 10 000 g mol À1 ), as a reference substance as it did not affect ice recrystallization in previous experiments. [16,17] An analysis of all experiments with additive concentrations 0.1 mg mL À1 is shown in Figure 2 b. The concentration-dependent median ice-crystal diameter after 2 h of annealing, d(c), can be described by a simple exponential model [Eq.…”

Antifreeze Properties of Polyglycidol Block Copolymers

“…[18][19][20][21][22][23] For instance, we described a new approach [22] to the design of block copolymers that mimic AFP. We illustrated that block copolymers with functional groups analogous to AFPs can influence the bulk structure of liquid water and ice and affect the crystallization kinetics of ice.…”