Tunable Thermosensitivity Of Amphiphilic Polymer Micelles Of Poly(Vinylcaprolactam)-b-Poly(ε-caprolactone) Block Copolymers

Novel amphiphilic thermo-responsive copolymers poly(vinylcaprolactam)-6-poly(s-caprolactone)(PNVCL-A-PCL) were synthesized, and their properties of micelles were investigated.PNVCL-b-PCLs were synthesized by ring-opening polymerization of ε-caprolactone (ε-CL) with hydroxy-terminated poly(N-vinylcaprolactam)(PNVCL-OH) as a macroinitiator. The PNVCL-OH was obtained by radical polymerization of N-vinylcaprolactam (NVCL) initiated by azobisisobutyronitrile (AIBN) with mercaptoethanol (HSCH2CH2OH) as chain transfer agents. The structures of the polymers were confirmed by IR,1H NMR, and the molar mass and its distributions were determined by gel permeation chromatography (GPC).The fluorescence technique was used to determine the critical micelle concentrations (CMC) of copolymer micelles solution. The factors affected the lower critical solution temperature (LCST) of the copolymers were studied by UV-visible analyses. The diameter and distribution of the micelles were characterized by dynamic light scattering (DLS) and the shape was observed by transmission electron microscopy (TEM). The results showed that these copolymers could self-assemble into nano-micelles in water. The CMC of copolymer solution and the size of micelles reduced with the increasing of the proportion of hydrophobic parts. The CMCs were in a range of2.6×10-2mg/mL to0.3×10-2mg/mL and the sizes of the particle were in a range of106nm to167nm. TEM images demonstrated the micelles are all spherical. On the other hand, the UV-vis measurement showed that these diblock copolymers exhibit a reproducible temperature-responsive behavior with a lower critical solution temperature (LCST) that is tunable by the block composition.