Construction of thermoresponsive SCKs through tuning the crystalline melting point of the core domain

Shell cross-linked knedel-like (SCK) block copolymer micellar nanoparticles were prepared from poly(acrylic acid-b-octadecyl acrylate-co-decyl acrylate) and studied as unique systems, having tunable core melting transition temperatures (Tm). Tm depression was accomplished by diluting octadecyl acrylate with the co-monomer decyl acrylate in the construction of the hydrophobic block segment of amphiphilic block copolymers of similar lengths and chemical compositions. Organization of those block copolymers into micelles and cross-linking throughout the shell then afforded a series of SCKs that exhibited core Tm values ranging from 3 to 40 °C. Confinement of the side-chain crystalline polymer chains within the core of the SCKs resulted in depression and broadening of the Tm values, which increased by ca. 5 °C when the shell was hydrated, as determined by differential scanning calorimetry measurements in the dry and 30 % (w/w) hydrated states. Passage through the melting transition was also observed for the SCKs dispersed in water, by dynamic light scattering experiments, which revealed an expansion and then collapse in hydrodynamic diameter over the temperature range of core melting. As the crystalline-amorphous core behaviors could be tuned over physiological temperature ranges, these nanoparticles are expected to be of utility as tunable drug delivery devices, with control over the kinetics and conditions of packaging and release.