Thermoreversible Poly(alkyl acrylates) Consisting of Self-Complementary Multiple Hydrogen Bonding

Abstract

The synthesis and characterization of novel self-complementary multiple hydrogen-bonded (SCMHB) polymers containing pendant 2-ureido-4[1 H ]-pyrimidone (UPy) units are described. SCMHB pendant polymers, poly(butyl acrylate- co -SCMHB methacrylate), were prepared via free radical copolymerization of butyl acrylate (BA) and a novel SCMHB methacrylate (SCMHB MA) monomer, which was synthesized via a quantitative coupling reaction between 2-isocyanatoethyl methacrylate (ICEMA) and methyl isocytosine (MIS) in DMSO. The glass transition temperatures of poly(BA- co -SCMHB MA) increased in a linear fashion as the SCMHB MA content increased. Thermogravimetric analysis of the copolymers exhibited an onset of weight loss at 217 °C. Solution viscosity analysis indicated that SCMHB pendant polymers strongly aggregated in nonpolar solvents, such as toluene and CHCl 3, and dissociated in polar solvents, such as THF. Based on melt rheological characterization, the melt viscosity of soluble SCMHB pendant polymers was an order of magnitude higher than that of PBA due to strong aggregation in the melt state. SCMHB pendant polymers exhibited thermoreversible characteristics, and complete dissociation in the melt state was observed at 80 °C, which was consistent with our earlier studies involving SCMHB-terminated poly(styrene) (PS), poly(isoprene) (PI), and PS- b -PI block copolymers. In addition, SCMHB units completely dissociated at 80 °C in toluene on the basis of 1 H NMR measurements. The 90° peel strength values for SCMHB-containing polymers increased as the SCMHB units increased due to the strong interaction of SCMHB units with the glass surface. Thin-layer chromatography indicated that the interaction of SCMHB pendant polymers with silica was more favorable compared to PBA homopolymer.