Microphase segregation of PEO-PAMAM linear-dendritic diblock copolymers

Transmission electron microscopy and X-ray scattering have been used to characterize the microphase segregation of linear - dendritic diblock copolymers in the bulk state. The dendritic block copolymers consisted of a linear poly(ethylene oxide) (PEO) block of 2000 molecular weight attached covalently to a polyamidoamine (PAMAM) dendron. The morphology and temperature dependence of diblocks containing dendrons of generations 1.0-4.0 was characterized. In addition, the dendritic end groups were functionalized with stearic acid to make amphiphilic linear - dendritic diblock copolymers. The morphology and temperature dependence of these materials was also characterized. Results indicate that the unfunctionalized diblocks exhibit a segregated melt state above the PEO melting point and that the PEO block undergoes confined crystallization below its melting point. The glass transition of the PAMAM block is below room temperature such that the PEO crystallinity is weakly confined by the PAMAM domains. The stearate functionalized diblocks also exhibit a segregated melt state at high temperature. However, at low temperatures both the stearate and PEO are crystalline and crystallization is strongly confined within lamellar domains.