Combining Renewable Gum Rosin and Lignin: Towards Hydrophobic Polymer Composites by Controlled Polymerization

Rosin polymer-grafted lignin composites were pre- pared via ''grafting from'' atom transfer radical polymerization (ATRP) with the aid of 2-bromoisobutyryl ester-modified lignin as macroinitiators. Three different monomers derived from dehydroabietic acid (DA) were used for execution of grafting from ATRP, while DA was separately attached onto lignin by a simple esterification reaction. Kinetic studies indicated con- trolled and ''living'' characteristics of all monomer polymeriza- tions. Thermal studies indicated that rosin polymer-grafted lignin composites exhibited glass transition temperatures in a broad temperature range from � 20 to 100 � C. The grafting of both DA and rosin polymers significantly enhanced hydropho- bicity of lignin. Static contact angle measurement of water droplets showed � 90 � for all these rosin modified lignin com- posites. X-ray photoelectron spectroscopy demonstrated that the surface of rosin-lignin composites was dominated with chemical compositions originating from the hydrocarbon rich rosin moiety. The impartation of hydrophobicity of rosin into lignin provided excellent water resistance of this class of renewable polymers, as all rosin-modified lignin com- posites showed water uptake below 1.0 wt %. V C 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 3728-3738, 2011