Constrained Crystallization And Hierarchical Self-assembly Of Semi-crystalline Bottlebrush Block Copolymers

Semi-crystalline bottlebrush block copolymers(SCBBCPs)combine the properties of bottlebrush block copolymers such as high grafting density of side chains,low-chain entanglement,extended main chain and the advantage of easy processing for crystalline polymers.This thesis studies the confined crystallization of SCBBCPs and its application in the preparation of one-dimensional photonic crystals(1D PCs)by bulk self-assembly.The norbornyl ester end-functionalized poly(ethylene glycol)(NB-PEG,M_n=2700)and poly(n-butylacrylate)(NB-Pn BA,M_n=3100)are synthesized via end-functionalization and atom transfer radical polymerization,respectively.The semi-crystallinebottlebrushblockcopolymers,PPn BA-b-PPEG(BBCP350-BBCP550),with main chain degree of polymerization(DP)350,400,450,500 and 550,were prepared by sequential ring-opening metathesis polymerization(ROMP)of the macromonomers.Constrained crystallization of PPn BA-b-PPEG are studied by isothermal crystallization at room temperature.The SCBBCPs are directly thermal self-assembled into first order lamellar structures of hundreds nanometers within a few minutes at 80?.1D PCs are formed after confined crystallization of PEG within the first lamellar microdomain at 25? to form second order lamellar structure of ca.13 nm,which increases the refractive index contrast of the first order lamellae.The prepared 1D PCs are structure memory,as they change reversibly from hierarchical lamellae to first order lamellae and disordered structures by temperature,and remember each structure at 25?,80?,and 90? and above temperatures,respectively.Owing to the structure memory property,the 1D PCs show multifunctional properties such as temperature sensitive,self-healing,re-moldable and recyclable,which shows applications in patterning,printing and anti-counterfeiting.The temperature controlled preparation of structure memory 1D PCs is environmentally friendly,low cost,and convenient for operating.In order to further study the main chain structure on the self-assembly of SCBBCPs,macromonomers with rigid norbornyl imide structure(HNB-PEG,M_n=2600;HNB-Pn BA,M_n=2200)are synthesized.And semi-crystalline bottlebrush block copolymers with hard main chain,H(PPn BA-b-PPEG)(HBBCP350),are prepared by ROMP.The effect of the rigid main chain structure on the confined crystallization of SCBBCPs and the fabrication of 1D PCs materials are investigated.It is shown that the crystallinity of HBBCP350 with more rigid main chain is significantly reduced to about 40%after confined crystallization.However,the rigidity of the main chain has less effect on the preparation of 1D PCs by the method of heating to 80? for thermal assembly and cooling to 25? for constrained crystallization,and 1D PCs with bright color are also obtained in this way.