GRAFT-COPOLYMERS OF LIGNIN WITH 1-ETHENYLBENZENE .2. PROPERTIES

The graft copolymerization of lignin and 1-ethenylbenzene was coinitia ted by lignin, calcium chloride, and hydrogen peroxide in dimethyl sul foxide solution. Conversion of 1-ethenylbenzene and yield of polymeriz ed product of 90% or more were obtained. The copolymerization reaction changes the hydrodynamic radius of the product. Grafting has changed the surface properties of the original lignin from hydrophilic to hydr ophobic. The copolymerization product is a thermoplastic material. Whi te rot Basidiomycete were able to biodegrade styrene (1-ethenylbenzene ) graft copolymers of lignin containing different proportions of ligni n and poly(1-phenylethylene). The polymer samples were incubated with white rot Pleurotus ostreatus, Phanerochaete chrysosporium, and Tramet es versicolor and brown rot Gleophyllum trabeum. White rot fungi degra ded the plastic samples at a rate which increased with increasing lign in content in the copolymer sample. Both poly(1-phenylethylene) and li gnin components of the copolymer were readily degraded. Poly(1-phenyle thylene) pellets were not degradable in these tests. Observation by sc anning electron microscopy of incubated copolymers showed a deteriorat ion of the plastic surface. Brown rot fungus did not affect any of the se plastics. The FTIR of the graft copolymers shows a series of charac teristic absorbance peaks from multisubstituted aromatic rings and a s trong poly(1-phenylethylene) (polystyrene) absorbance peak from monosu bstituted aromatic rings. Subtraction of copolymer spectra taken after 50 days of incubation with the four tested fungi from spectra taken b efore incubation shows the loss of functional groups from the copolyme r. The graft copolymer with long poly( 1-phenylethylene) side chains i s a macromolecular surface active material because in each graft molec ule, a long hydrocarbon side chain has been grown off of a natural (ox yphenyl)propyl backbone. Surface activity of the graft copolymers is i ndicated by their capacity to form stable emulsions between incompatib le fluid phases and to adhesively bond to wood surfaces. Dynamic conta ct angle measurement using the Wilhelmy plate technique shows that the graft copolymers change the contact angle of water on wood from 50 to 110 degrees. The copolymerization product and its fractions have a co upling effect in the connection of wood to poly(1-phenylethylene). Lap shear strengths increase 56%, from 1826 to 2840 kPa, when the wood is coated with a graft copolymer containing 51.7% lignin.