Discrete Diblock Copolymers With Isomeric Side Chains

Molecular topology is an essential parameter that regulates the self-organization of block polymers,which has not yet been well exploited and appreciated in block polymers due to the lack of precise and efficient modulation methods.In this thesis,we rationally designed three categories of discrete block copolymers with the same composition but varied alkyl side-chain topology(linear,branched,and cyclic)through a combination of the step-growth approach and highly efficient coupling reactions and scrutinized the influence of side chain on the selfassembly behaviors.The main contents are as follows:(1)With discrete oligo-lactide and oligo-(β-dodecyl malate)as building blocks,discrete diblock copolymers bearing linear side hydrocarbon chains were modularly synthesized.The self-assembly behaviors were characterized by small angle X-ray scattering.Diverse ordered structures,including conventional phases(HEX and BCC)and unconventional spherical lattices(including Frank-Kasper A15,σ,and DDQC)were identified by tuning the composition.(2)Discrete diblock copolymers with branched side chains were prepared by adopting oligo-(β-2-butyl octyl malate)as the building block.Similar ordered structures were observed,including HEX,A15,σ,DDQC,and BCC.Compared with the linear isomers,introducing branched side chains shifts the phase boundary between the spherical and columnar phases.The lattice dimension shrinks and phase stability reduces,as compared with the linear side-chain counterparts.(3)Discrete diblock copolymers with cyclic side chains were obtained by using oligo-(β-dodecacyclic malate)as the building block.The self-assembly behaviors of these copolymers were found to be significantly different from the linear and branched isomers.No complex spherical phase was observed.The lattice size of the cyclic side-chain copolymers is dramatically reduced,as well as the phase stability.