Architecture Design of Hyperbranched Polyethylene Enabling Thermal Diode Based on Poly(High Internal Phase Emulsion)
Supervisor:wang wen jun
Hyperbranched Polyethylene(HBPE)contains highly branched chains,whose molecular structure is spherical and without chain entanglements.Its crystallinity is far lower than industry polyethylene,having low glass transition temperature,low melting pointing,and 3D structure.Furthermore,HBPE can be easily modified by copolymerization.So far,because catalytic systems of HBPE are sensitive to the functional groups,modification with highly reactive and amphiphilic groups is a long-term challenge.In this thesis,a universal strategy for the functionalization of HBPE via a combination of copolymerization and post modification is developed.Porous polymers(PolyHIPEs)made from high internal phase emulsion(HIPE)have high porosity and fine interconnected pore structures,widely used in many applications such as catalysis and separation.Poor mechanical property due to large surfactant dosage during fabrication can’t meet the requirement of further application.This thesis dramatically increases the mechanical strength through minimizing surfactant dosage by high efficient HBPE Pickering emulsifier,Thermal diodes are made from PolyHIPEs as skeleton of phase change materials.Corresponding contents are divided into three parts:(1)Reactive amphiphilic HBPEs with epoxy groups made by one step copolymerization are used in enzymatic catalysis in organic solvent.Bi-phase system is firstly introduced for synthesizing HBPE-enzyme nanocomposite,which can improve enzymatic activities in organic solvent with good stability in ambient temperature and recycle ability.(2)HBPE Pickering surfactants synthesized by copolymerization and post modification have the advantages of both surfactant and Pickering emulsifier,can stabilize HIPE.Enhanced mechanical strength is obtained by decreasing surfactant residual in skeletal polymer,for the first time,reaching the theoretical maximum value of PolyHIPE.(3)Composite of skeletal PolyHIPE impregnated with phase change materials has a large step of thermal conductivity as it crosses the phase transition temperature,can maintain its shape and solid-state nature during through the entire range of working temperatures.Two generations of phase change thermal diode are made based on the composite with highest thermal rectification in literature.