The influence of pH, hydrolysis and degree of substitution on the temperature-sensitive properties of polyaspartamides

Temperature-sensitive polyaspartamide obtained by the aminolysis reaction of polysuccinimide with isopropylamine has been proposed as a good material for biomedical applications. The polymer is susceptible to hydrolysis producing carboxyl groups; thus the temperature-sensitive behavior of the polymer depends on pH. A set of polyaspartamides was synthesized with different degrees of hydrolysis (DH) and substitution (DS). The influence of DH, DS and pH on the lower critical solution temperature (LCST) of the polyaspartamides was studied. The LCST of the polyaspartamides increases as the pH increases and at the same pH the polymer with higher DH presents a higher LCST. Also, at the same pH an increment in the DS produces a decrease in the LCST. These tendencies are explained by the presence of a carboxylate group on the polyaspartamide structure. The behaviors can be tailored as functions of DS and DH enabling the use of temperature-sensitive polyaspartamide in different biomedical applications where pH and/or temperature changes will trigger a drug delivery. © 2018 Society of Chemical Industry.