The physicochemical properties of poly(2-alkyl-2-oxazoline)s (PAOX) depend on the alkyl side chain length. As the alkyl side chain length decreases, LCST of aqueous solutions increases, glass transition temperature (Tg) increases and bulk crystallization is significantly hindered. Among PAOX having shorter side chains, poly(2-ethyl-2-oxazoline) (PEOX) is the only member whose bulk crystallization was previously not reported. We have shown that self-assembled crystalline PEOX fibers form (Fig. 1) when aqueous PEOX solutions are kept above the cloud point temperature (Tc) for long times (days to weeks). Figure 1. <img src='https://acs-archive-assets2.s3.amazonaws.com/se_sw_rm/uploads/62466_katie.jpg' alt='' /> In order to understand the role of alkyl side chain length in PAOX crystallization and the factors affecting the formation of crystalline fibers in aqueous solutions, we have investigated PAOX crystallization in bulk and the self-assembly in aqueous solutions as a function of alkyl chain length, temperature, molecular weight and ionic strength. We identified different crystallization behavior depending on the length of the alkyl side chain. The self-assembly into water insoluble fibers above Tc, a slow crystallization process, was enhanced by the addition of various sodium salts. The specific anion effects on Tc of aqueous PEOX solutions will be presented and the contribution of different mechanisms to phase separation at Tc and self-assembly will be discussed.

Poly(2-alkyl-2-oxazoline)s: Bulk crystallization and solution self-assembly

248th National Meeting (2014)

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