Thermo‐ and pH‐Responsive Polymersomes of Poly(α,β‐N‐substituted‐DL‐aspartamide)s

Abstract

AbstractMaterials that can respond to multiple stimuli, such as temperature and pH changes, are of considerable interest for applications in drug delivery systems. Notably, α,β‐[poly(2‐hydroxyethyl)‐DL‐aspartamide] is a potentially useful material for such applications. This study investigated the temperature and pH responsiveness of polymers structurally similar to α,β‐[poly(2‐hydroxyethyl)‐DL‐aspartamide], namely, poly(α,β‐N‐substituted‐DL‐aspartamide)s, in aqueous media. These polymers were derived from polysuccinimide (PSI), which was first synthesized via acid‐catalyzed bulk polycondensation of L‐aspartic acid (L‐ASP) in the presence of 85% o‐phosphoric acid under N2. Two primary amino alcohols, 4‐aminobutanol (4AB) and 6‐aminohexanol (6AH), were then respectively utilized to modify PSI to form poly (α,β‐N‐substituted‐DL‐aspartamide)s via aminolysis. Different ratios of these two amino alcohols were used to modify the polymer to produce a series of copolymers with lower critical solution temperatures ranging from 53–28°C when dispersed in aqueous media. Moreover, the properties of the poly(α,β‐N‐ substituted‐DL‐aspartamide)s in aqueous solution were affected by pH changes. The morphology of the particles formed by these amphiphilic polymers was observed using scanning electronic microscopy and transmission electronic microscopy, and the particles were found to be polymersomes with shell and hollow core structures and diameters of 0.5–1 μm. Other properties of this series of self‐assembly copolymers were also characterized. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012