Several thermogelling block copolymers have been developed for biomedical applications, such as drug or cell delivery carriers. The amphiphilic block copolymers containing hydrophilic and hydrophobic segment exhibit thermal phase transition mediated by hydrophobic interactions among hydrophobic segments. The formation of a crystalline domain via hydrophobic interactions is sensitive to the identity of the hydrophobic segment. Thus, the functional groups on amphiphilic block copolymers can engage in intra- and intermolecular interactions to effect hydrophobic interactions.
The aim of this thesis is to prepare an unique amphiphilic diblock copolymer with thermogelling property. In this thesis, MPEG-b-PCL diblock copolymers are selected in an attempt to prepare thermogelling polymer system via controllable intra- and intermolecular interactions.
In the chapter 2, MPEG-b-PCL diblock copolymers with anionic and cationic groups into the hydrophobic PCL chain end positions are prepared and examined at the thermogelling transitions as a function of temperature. MPEG-b-PCL diblock copolymers with anionic and cationic groups exhibited the formation and destruction of a structured gel network of MPEG-b-PCL diblock copolymers, depended on the crystallinity and hydrophobicity of the PCL domains in aqueous media.
In the chapter 3, MPEG-b-(PCL-ran-PLLA) diblock copolymers with various groups into the hydrophobic PLLA chain pendant positions are prepared and examined at the thermogelling transitions as a function of temperature. Intra- and inter-molecular interactions among hydrophobic PCL and PLA domains can stabilize or destabilize aggregation among the hydrophobic segments, which is a prerequisite for achieving thermogelling polymer system.
In conclusion, these results show that novel amphiphilic diblock copolymers prepared in this work may serve as a thermogelling polymer system with an adjustable temperature-responsive window.