Well defined graft copolymers and end functional materials: synthesis, characterization and adhesion studies

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Date
1993
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Virginia Tech
Abstract

This research focuses on the utilization of two living polymerization methods, anionic and group transfer, for the synthesis of well defined end functional materials and graft copolymers. Group transfer polymerization was utilized to synthesize acrylic terminal poly(methyl methacrylate) (PMMA) macromonomers of controlled molecular weight and narrow molecular weight distribution. A systematic series of PMMA macromonomers were copolymerized with 2-ethylhexyl acrylate to afford poly(2-ethylhexyl-g-methyl methacrylate) copolymers. These copolymers were synthesized in high yields with a high degree of incorporation of the PMMA macromonomer. These graft copolymers showed little or no phase mixing between the two components as evidenced by differential scanning calorimetry.

It was determined by optimization studies that the reaction was complete within 50 hours at 65° C. Increases in initiator concentration surprisingly did not significantly effect homopolymerizations of 2-ethylhexyl acrylate with respect to molecular weight while the efficiency of incorporation of the macromonomer into the graft copolymers increased.

End functional hydrogenated poly(butadiene) (HPBd) materials and HPBd-containing graft copolymers were synthesized using anionic polymerization methods. These materials were tested for their ability to act as adhesion promoters between poly(propylene)/EPDM and cycloaliphatic polyurethane coatings. Hydroxyl or carboxyl end functional materials were synthesized where molecular weight and chain microstructure were syStematically varied. Effective adhesion was achieved when the molecular weight of the polymer was approximately 20 kg/mol, the polymer was hydrogenated, contained 90 mole percent or greater 1,2- content in the poly(butadiene) precursor, and contained a functional end group, which may be either hydroxyl or carboxyl.

To increase the concentration of functional groups over the above materials graft copolymers were utilized. Acrylic terminal HPBd macromonomers were synthesized and copolymerized with butyl acrylate in combination with either N,N-dimethylacrylamide (DMAA), 2-hydroxyethyl methacrylate (HEMA), methacrylic acid (MA), or t-butyl methacrylate (TBMA). Systematic compositions of these graft copolymers were synthesized and tested for adhesion. The acidic containing graft copolymers provided the most positive adhesion results. In one case the hydroxyl containing material also gave positive adhesion results. The DMAA containing materials failed in all cases. The TBMA route allowed for greater control over the composition of the acidic graft copolymers.

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