PREPARATION OF CROSS-LINKED ALIPHATIC POLYESTER AND APPLICATION TO THERMORESPONSIVE MATERIAL

The aim of this study is to investigate the application of a crystalli ne polymer network to a thermo-responsive material. To achieve this pu rpose, cross-linked aliphatic polyesters containing a poly-epsilon-cap rolactone (poly-CL) segment were prepared from tetrafunctional star-sh aped macromonomers. The macromonomers were synthesized by ring-opening polymerization of CL and L-lactide (LA) initiated with pentaerythrito l followed by condensation with methacryloyl chloride to introduce a f unctional group at the chain ends. The cross-linked polyester membrane s were prepared by way of a radical polymerization of the macromonomer s with visible light irradiation in the presence of initiator and sens itizer. The obtained materials, which consisted of CL homopolymer and LA/CL block copolymer, exhibited a phase transition temperature derive d from the melting of poly-CL segment. The transition temperatures of the macromonomers and the corresponding cross-linked polyesters depend ed on the length of poly-CL segment. In order to examine the thermo-re sponsive properties, the permeation of a model drug, indomethacin, thr ough the membrane composed of cross-linked polyester was investigated by using a 2-chamber diffusion cell. The permeability of the drug incr eased steeply at around the phase transition with increasing temperatu re. In addition, the relationship between the degree of crystallinity and the increase of the drug permeability was discussed. From the anal ysis of permeation profiles, it was revealed that the partition of the drug from the donor phase to the membrane surface considerably increa sed above the phase transition. Also, the reversible control of the dr ug permeation through the membrane in response to the repeating temper ature change (20 degrees C and 40 degrees C) was observed.