A combinatorial approach to studying the effects of N-alkyl groups on poly(N-alkyl and N,N-dialkylacrylamide) solubility.

Soluble polymers including poly(N-alkylacrylamide)s with low mole percent loadings of pendant groups are of interest in applications in catalysis, synthesis, sequestration, and soluble affinity chromatography where their thermal and phase-dependent solubility facilitates purification and separation. This work describes a library synthesis and study of the effects of polymer composition on the phase-selective solubility of dye-labeled poly(N-n-octadecylacrylamide-co-N-n-butylacrylamide) copolymers. To study the relative importance of n-octadecyl versus n-butyl groups, copolymers with different ratios of n-octadecylacrylamide and n-butylacrylamide but with similar degrees of polymerization and polydispersity were prepared by a split-pool synthesis using a highly soluble poly(N-acryloxy-2-dodecylsuccinimide) as the precursor. Polymer sequestrants were used to remove excess amines and the byproduct N-hydroxyl-2-dodecylsuccinimide without fractionation of the polyacrylamides. Other studies of dye-labeled poly(N,N-dialkylacrylamide)s prepared by the polymerization of N,N-dialkylacrylamides with methyl, ethyl, propyl, butyl, pentyl, and hexyl N-alkyl groups in a variety of thermomorphic or latent biphasic polar/nonpolar solvent mixtures showed that poly(N,N-dialkylacrylamide)s like poly(N-alkylacrylamide)s have phase-selective solubility that is highly dependent on the size of the N-alkyl group.