Semisegmented Amphiphilic Polymer Conetworks: Synthesis and Characterization

Semisegmented amphiphilic polymer conetworks (APCNs) based on the hydrophilic monomer 2-(dimethylamino)ethyl methacrylate (DMAEMA), the hydrophobic monomer methyl methacrylate (MMA), and the hydrophobic cross-linker ethylene glycol dimethacrylate (EGDMA) were prepared using group transfer polymerization in a two-step procedure that involved the synthesis of linear polyDMAEMA or polyMMA arms, followed by their cross-linking using a mixture of EGDMA with either MMA or DMAEMA, respectively. Four semisegmented APCNs with polyMMA arms with degrees of polymerization (DP) of 10, 20, 30, and 40 and three with polyDMAEMA arms with DPs of 10, 20, and 30 were prepared. The sol fraction extracted from the APCNs, the percentage of linear polymer in the sol fraction, and the molecular weights of the branched fraction of the extractables increased as the DP of the arms increased. The degrees of swelling (DSs) in water of all semisegmented APCNs increased with decreasing pH and increasing percentage of DMAEMA hydrophilic units. Despite the rather imperfect, semisegmented placement of the dissimilar units, extensive small-angle neutron scattering (SANS) experiments in D2O indicated that nanophase organization did take place within these APCNs and persisted, in many cases, even at full ionization of the hydrophilic monomer repeating units. The SANS profiles were also used to calculate the spacings between the scattering centers, which were found to increase with the content in the DMAEMA units and their degree of ionization.