The Influences Of Monomer Structure And Solvent On The Radical Copolymerization Of Tertiary Amine And Pegylated Methacrylates

Tertiary Amine Methacrylates (TAMAs), such as 2-(N,N-diethylamino)ethyl methacrylate (DEAEMA) and 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA), and PEGylated (macro)monomers, such as 2-ethoxyethyl methacrylate (EEMA(1)) and poly(ethylene glycol) methyl ether methacrylates with 9 and 23 units (PEGMA(9) and PEGMA(23), respectively), are two families of monomers frequently used in the synthesis of stimuli-responsive and biocompatible materials. They, along with methyl (MMA) and butyl (BMA) methacrylate, were used to synthesize a minilibrary of copolymers, namely poly(DEAEMA-co-EEMA(1)), poly(DEAEMA-co-PEGMA(23)), poly(DMAEMA-co-PEGMA(9)), poly(DMAEMA-co-PEGMA(23)), poly(DEAEMA-co-MMA), and poly(BMA-co-PEGMA(9)). The rate of copolymerization increased as the length of the PEG-side chain is decreased, and was higher for DEAEMA compared to DMAEMA systems. The estimated values of the reactivity ratios are: r(DEAEMA) = 0.61 +/- 0.06 and r(EEMA1) = 0.92 +/- 0.09, r(DEAEMA) = 0.71 +/- 0.15 and r(PEGMA23) = 1.05 +/- 0.21, r(DMAEMA) = 0.83 +/- 0.01 and r(PEGMA9) = 1.08 +/- 0.02, r(DMAEMA) = 0.52 +/- 0.09 and r(PEGMA23) = 0.76 +/- 0.14, and r(BMA) = 0.55 +/- 0.13 and r(PEGMA9) = 0.38 +/- 0.09; p-dioxane at 70 degrees C: r(DEAEMA) = 0.91 +/- 0.12 and r(PEGMA9) = 0.75 +/- 0.09; and tetrahydrofuran at 66 degrees C: r(DEAEMA) = 0.96 +/- 0.13 and r(PEGMA9) = 0.81 +/- 0.11. While there was no difference in relative reactivity between the two amine-functional monomers when copolymerized with PEGylated methacrylates, the increased relative activity of the TAMAs compared to BMA is attributed to the formation of a cyclic intermediate. Additionally, as the PEG side-chain length is extended, the reactivity ratios for the amino monomers decreased. Finally, although a higher content of DEAEMA is incorporated in the copolymer for the poly(DEAEMA-co-MMA) when a more polar solvent is used, no differences were observed in the Mayo-Lewis plots for the poly(DEAEMA-co-PEGMA(23)) using p-dioxane, tetrahydrofuran and ethanol.