Synthesis and Bulk Self-Assembly of Well-Defined Binary Graft Copolymers

Six binary graft copolymers were synthesized, and their graft segregation in bulk was investigated. The copolymers were prepared by a one-pot method involving the quantitative grafting of alkyne-end-functionalized poly(n-butyl acrylate) (PBA-C CH) and poly(2-cinnamoyloxyethyl methacrylate) (PCEMA-C CH) onto poly(3-azide-2-hydroxypropyl methacrylate) (P(GMA-N-3)) via click chemistry. Of these copolymers, three had a total PBA and PCEMA molar grafting density g of similar to 20%, and their PBA volume fractions V-B among PBA and PCEMA varied between 28% and 57%. V-B was constant at similar to 57%, while g varied between 9.8% and 29.5% for the other three samples. Bulk films were obtained by slowly evaporating the solvent from cast solutions of these copolymers. These films were then annealed above the glass transition temperatures of PBA and PCEMA to facilitate graft segregation. The graft segregation patterns were examined by performing transmission electron microscopy (TEM) analysis of thin sections of these films. The TEM results suggested that the grafted PBA chains formed a disordered wormlike phase in a PCEMA matrix at V-B = 28%. At V-B = 42% and 57%, PBA and PCEMA seemed to form alternating lamellae. In the former case, the PBA layers were thinner than the PCEMA layers, while the PBA layers were thinner in the latter case. All three samples with V-B similar to 57% probably possessed a lamellar morphology. The periodicity of the lamellae increased and the long-range ordering deteriorated as g increased.