Preparation of Thiolated Polyvinyl Alcohol Hydrogels Bhuvanesh Gupta, 1 Sadiya Anjum, 2 Saiqa Ikram 2 1 Bioengeeniring Laboratory, Department of Textile Technology, Indian Institute of Technology, New Delhi-110016, India 2 Department of Chemistry, Jamia Millia Islamia (Central University), New Delhi-110025, India Correspondence to: B. Gupta (E-mail: bgupta@textile.iitd.ernet.in) ABSTRACT: The esterification reaction of polyvinyl alcohol (PVA) with thioglycolic acid (TGA) in the presence of sulfuric acid as a catalyst offers an attractive route to develop thiolated functional material. During esterification maximum thiol content of 3.9 mmol/ g was achieved. It was observed that the esterification is significantly influenced by the reaction conditions, such as TGA concentra- tion, reaction time, reaction temperature and reactant concentration. Sulfuric acid had considerable influence on the thiolation. The thiol content was found to increase with the reaction temperature but showed significant increase beyond 60  C. The swelling decreases with the increasing reaction temperature indicating the role of crosslinking during the thiolation at higher temperature. Suitable conditions for the modification of PVA via thiolation have been investigated. The involvment of thiol group in the PVA matrix was confirmed by ATR-FTIR spectra. The micro analysis of sulfur in sample by EDX analysis showed the sulphur content of 3.7%. V C 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 000: 000–000, 2012 KEYWORDS: functionalization of polymers; hydrophilic polymers; swelling Received 6 August 2012; accepted 20 November 2012; published online DOI: 10.1002/app.38856 INTRODUCTION Polymers obtained by introducing new functional groups in their structure may be used for the recovery of heavy metal ions from water. 1 Modification of polymers by chemical reaction is an inter- esting domain of functional material. The most studied polymers for the removal of metals include carboxylic, phosphoric, sulfonic, or ammonium groups in their structure. Interactions of metal ions with hydrophillic polymers are mainly due to electrostatic forces and the formation of coordinating bonds. Other weak interactions may appear such as trapping metal ions in the bulk of the polymer phase. 2 Among these hydrophilic polymers, polyvi- nyl alcohol (PVA) is the most interesting polymer that has been studied extensively in diverse areas of technology development. 3–5 PVA is soluble in water where the optimum conditions for disso- lutions are primarily governed by the degree of hydrolysis, molec- ular weight, particle size distribution and crystallinity. From the previous literature, same studies are available for the removal of heavy metal ions from water with various PVA derevatives. 6–11 To increase the potential use of PVA, modification could be per- formed by various routes and it is possible to improve properties such as water solubility, metal ion binding capability and selectiv- ity. 12 Esterification of PVA by reaction with various acid chlorides or acid anhydrides to develop functional material. 13–17 Heavy metals have strong affinity toward mercaptan (thiol) groups existing in biomolecules, such as amino acids, peptides, and proteins including some enzymes. 18,19 Based on the above understanding, thioglycolic acid (TGA) may be used for the modification of PVA by the involvement of thiol as additional groups. Thiols are stronger acids than relevant alcohols and phenols. Sulfur group will easily react with bases, acid, ketones or halogens. Where as the carboxylic acid of TGA will preferen- tially react in the presence of alcohol or amines. TGA has been used mainly as polymer modifiers and polymer stabilizers. 20 Dicharry et al., reported the multifunctional macromolecular thiol-PVA (TPVA) obtained by esterification of PVAwith 3-mer- captopropionic acid and used it as a wheat gluten reactive modifier. 21 Moreno et al. reported the esterification reaction in between hydroxyl group of PVA and carboxylic group function- alized gold nanoparticles which were synthesized by the reaction of mercaptoundecanoic acid and hydrogen tetrachloroaurate. 22 The aim of the present work is the preparation of functional TPVA by imparting ASH group into a PVA frame work. The op- timum processing conditions were investigated by single factor experiment with material ratios, the amount of catalyst, reaction temperature and reaction time to serve as targets. The structural changes of TPVA were observed from Attenuated Total Reflec- tance-Infrared Spectroscopy (ATR-IR) spectroscopy and were quantified by Volhard’s silver nitrate method. The micro analysis of the samples have been studied by Energy Dispersive X-ray Microanalysis (EDX). The performance of derived TPVA as V C 2012 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM WILEYONLINELIBRARY.COM/APP J. APPL. POLYM. SCI. 2012, DOI: 10.1002/APP.38856 1