Self Assembled Hydrophobic Nanoclusters of Poly(methyl methacrylate) Embedded into Polyvinyl Alcohol Based Hydrophilic Matrix: Preparation and Water Sorption Study Sandeep Kumar Shukla, 1 A. Wasif Shaikh, 2 Nikhil Gunari, 3 A. K. Bajpai, 1 R. A. Kulkarni 2 1 Department of Chemistry, Bose Memorial Research Laboratory, Government Autonomous Science College, Jabalpur 482 001, Madhya Pradesh, India 2 Polymer Science and Engineering Division, National Chemical Laboratory, Pune 411 008, Maharashtra, India 3 Institute of Physical Chemistry, University of Mainz, Mainz D-55099, Germany Received 16 March 2008; accepted 9 August 2008 DOI 10.1002/app.29155 Published online 22 October 2008 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Hydrophilic matrices containing nanosized clusters of hydrophilic moieties have demonstrated poten- tial applications in biomedical field. A novel hydrogel con- taining nanosized domains (20–35 nm) of hydrophobic moieties of poly(methyl methacrylate) (PMMA) was pre- pared by grafting crosslinked poly(acrylic acid-co-methyl methacrylate) chains onto polyvinyl alcohol (PVA) back- bone using an efficient redox system. The graft copolymer- ization process was investigated to observe the influence of gel components on the kinetic parameters of grafting such as rate of grafting (R g ), grafting yield (G y ) and graft- ing efficiency (G e ). The prepared graft nanohydrogel was evaluated for its water sorption potential under varying chemical composition of the gel and changing pH, temper- ature, and ionic strength of the swelling bath. The swelling process was also examined mechanistically and diffusion constants (D) of water molecules through the swellable nanohydrogel were also evaluated. V V C 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 1300–1310, 2009 Key words: hydrophilic polymers; nanocomposites; graft copolymers; swelling INTRODUCTION Discovery of water retaining materials with prede- signed structures has formed the very foundation of advanced biomedical and pharmaceutical sciences. 1 Commonly coined as ‘‘nanohydrogels’’ or ‘‘smart materials,’’ this unique class of macromolecular fam- ily owes a great number of applications such as con- trolled drug delivery systems, 2–4 soft contact lenses, 5 artificial implants, 6 actuators, 7 wound healing dress- ings, 8 agrochemical release carriers, 9 water purifica- tion devices, 10 etc. Their sensitive response to external stimuli such as pH, 11–13 temperature, 14–16 ionic strength, 17 magnetic field, 18,19 electric field, 20–22 ultraviolet light, 23 etc. and internal stimuli like chemical architecture, 24,25 initiators conditions, 26 etc. enable them to deserve as a potential candidate in biomaterial applications. Recent past has witnessed continuing efforts to de- velop compatible materials with negatively charged surfaces for being used as artificial vessels with superior blood compatibility. Most of the studies were aimed at attempting to understand the blood compatibility of foreign materials from the view point of protein adsorption and cell adhesion 27 and it was shown that the blood compatibility is affected by various properties of the material surface, for example, surface charge, wettability, surface free energy, topography or roughness, and presence of specific chemical groups on the surface. 28 Moreover, it has been pointed out that the water structure on the surface of the material is one of the most impor- tant factors affecting blood compatibility. 29 In spite of the fact that a large number of investigations have been done to explore the possible factors responsible for blood compatibility of a material, a concrete con- clusion has not yet emerged. The fundamental property to which all such bio- medical applications are credited lies in swelling of the nanohydrogels when they come in contact with an aqueous environment. 30 A study of the dynamics of water sorption by nanohydrogel, therefore, is of much importance as it not only monitors the pro- gress of the swelling process, but also gives an insight into the mechanism of water transport, Journal of Applied Polymer Science, Vol. 111, 1300–1310 (2009) V V C 2008 Wiley Periodicals, Inc. Correspondence to: A. K. Bajpai (akbmrl@yahoo.co.in or akbajpailab@yahoo.co.in). Contract grant sponsor: Department of Science and Technology (Major Research Project), Government of India, New Delhi; contract grant number: SP/S1/G-11/ 2001.