Methyl acrylate

The library of PBAEs was synthesized by adding primary amines to diacrylate compounds (1.2:1 molar ratio of diacrylate:amine) at 90 °C for 24h (Scheme 1A). These specific monomers were chosen so that single carbon changes to the backbone monomers and to the side chain monomers could be evaluated in the synthetic polymers. In a second step, the base polymers were end-capped by end-capping amines (at 10-fold molar excess of amine to diacrylate termini) at room temperature for 24 hours (Scheme 1B). These end groups were chosen so that the presence of small molecule functional groups could be evaluated and compared across base polymers with differential structure. Eight diacrylate bases, 4 amino alcohol side chains, and 10 primary-amine containing end-groups were used to synthesize 320 total polymers (Scheme 1C). In order to more closely match the underlying structure to the naming convention used, we have chosen a separate naming convention from previous studies. Here, the number after “B” (for “base”) corresponds to the number of carbons between acrylate groups in the diacrylate, so B3 means than there are 3 CH₂ units between acrylate groups in the diacrylate base. The number after “S” (for “side chain”) corresponds to the number of carbons between the amine group and the hydroxyl group in the side-chain. Previous top-performing base polymers termed “C32”, “C28” ²⁴ correspond to B4-S5 and B4-S4 respectively. The “E” (for “end group”) refers to which end-modifying amine was chosen; they are organized into structurally similar groups but the numbers are simply sequential. The modifier “m” refers to an added methyl group (so B3m has an added methyl group compared to B3) and the modifier “o” to an added hydroxyl group (so S3o has an added hydroxyl group compared to S3). Every base polymer was characterized with respect to its base polymer molecular weight. Weight-averaged molecular weights of the polymers in the library ranged from 2,000 to 48,000, and number-averaged molecular weights ranged from 1,500 to 12,000 (Figure 1, Table S2). While many of the base polymers (8/32) had a weight-averaged molecular weight (Mw) of approximately 10,000 Da (+/− 2,000 Da), some polymers had an especially high Mw (40–50,000 Da, such as B4-S4, B6-S4, and BL2-S3o), and others had an especially low MW (under 3,000, such as BL1-S3 and BH1-S4). The viscosity of the starting monomers appears to have a significant effect on the molecular weight obtained using this synthesis protocol. S3o is relatively more viscous than S3, S4 or S5; polymers synthesized with S3o all had Mw of less than 9,000 Da, except for BL2-S3o. S4 containing polymers with simple hydrocarbon backbones (B3, B3m, B4, B5, B6) all had Mw of greater than 10,000. BL1, BL2, and BH1 all needed to be solvated in order to be effectively mixed with the amino alcohol side chains, and the resulting polymers in general were all smaller than the Mw obtained from the neat synthesis protocol.