Hydration‐mediated effects of saccharide stereochemistry on poly(N‐isopropylacrylamide) gel swelling

Abstract

To shed new light on the mechanisms of saccharide stereochemistry effect on macromolecules in aqueous solutions, we studied the effect of three monosaccharide stereoisomers, glucose, galactose, and mannose, on the swelling of Poly(N‐isopropylacrylamide) (PNIPA) hydrogels. We equilibrated PNIPA hydrogels in sugar solutions of different concentrations at 25 °C, and determined gel volume and mass swelling ratios, and sugar concentration imbalance. The volume‐phase‐transition occurred at molal concentrations of 0.587 ± 0.004 (galactose), 0.724 ± 0.003 (glucose), and 0.846 ± 0.004 (mannose). The same order of sugars emerged for the gel‐swelling and the magnitude of the sugar concentration‐imbalance, which correlated with sugar isentropic molar compressibility and hydration number. The more hydrated the sugar, the worse a cosolvent it is for the polymer, hence the larger the deswelling and the more negative the sugar concentration imbalance. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011

Soluting-in and soluting-out of water-soluble polymers in aqueous carbohydrate solutions studied by vapor pressure osmometry

“…They observed that the swelling of polyacrylamide gels, which are hydrophilic polymers as PEGs, increases with rising glucose concentrations and there is an enthalpically favorable interaction between glucose and polyacrylamide [4]. However, based on their results, sugars exert shrinkage and soluting-out effects on poly(N-isopropylacrylamide) gels, which are hydrophobic polymers as PPG [6]. These observations are in close agreement with the results of the present study of the carbohydrates soluting effects on aqueous polymer solutions.…”

“…Livney et al [4,6] studied the effect of carbohydrates on the swelling of polyacrylamide and poly(N-isopropylacrylamide) gels. They observed that the swelling of polyacrylamide gels, which are hydrophilic polymers as PEGs, increases with rising glucose concentrations and there is an enthalpically favorable interaction between glucose and polyacrylamide [4].…”

“…They have received a huge interest for delivery of macromolecular drugs, vaccine development and cosmetic industry [2,3]. Carbohydrates may exert significant influence on the stability and behavior of aqueous polymeric systems in foods and in other fields of application [4][5][6]. For instance, polyethylene glycols (PEGs) are used as plasticizers in film-coating formulations for food supplements and pharmaceutical products (tablets and capsules) [7].…”

Unexpected Large Depression of VPTT of a PNIPAM Microgel by Low Concentration of PVA

“…The effects of saccharide on the LCST of PNIPAM were therefore explained by their effects on the structured water around the polymer. They may immobilize water molecules near them, weaken hydrophobic hydration of the polymer, and consequently enhance the hydrophobic interaction between the polymer chains . The different ability of different saccharides to lower LCST was related with the number of equatorial hydroxyl groups in the saccharide molecules, because the equatorial hydroxy groups of saccharide molecules interact more easily with water clusters around the hydrophobic isopropyl groups and thus change the situation of polymer hydration …”

Thermoresponsivity of poly(N-isopropylacrylamide) microgels in water-trehalose solution and its relation to protein behavior

“…In this context, it is worth studying the specific effect of this biologically relevant sugar on the collapse of PNIPAM-based architectures. The PNIPAM-watertrehalose ternary system is much less investigated both experimentally and numerically as compared to any other ternary system of the same polymer, including those containing saccharides [44][45][46][47][48][49]. Experimental investigations using cloud point measurements, differential scanning and isothermal titration-microcalorimetry [44,46], report a significant decrease of LCST of PNIPAM chains in aqueous solution on increasing mono-and disaccharide concentration, finding a good correlation of the saccharide hydration with the decrease of LCST, and hence with the promotion of the globular compact state of the polymer.…”