| Demands for all aspects of human daily life,such as environment,energy and resource,are constantly rising with the third revolution of science and technology.Therefore,the development and utilization of innovative technologies and renewable energy have never stopped to exploit more comfortable,clean-living environment and convenient smart products.Phase change materials(PCMs)are considered as one of the most effective ways to achieve an adjustment of thermal regulation functions within the desired temperature range and reconcile the supply and demand mismatch of renewable energy through reversibly storing and releasing thermal energy as latent heat.It shows many attractive advantages such as low cost,environmentally-friendly and reusable,called as“portable air conditioner”.As a consequence,PCMs have been widely employed in various areas,for example recovery and utilization of waste heat,thermoregulation of smart building construction,solar-thermal conversion and storage,and thermal management of textiles or astronautics.However,the defects of phase change materials,such as morphological instability,high brittleness,poor thermal conductivity,difficulty in forming and no spinnability,limit their application scope.In order to solve the above problems,in this study,the different kinds of cellulose were employed as matrix,tetradecyl acrylate(A14),hexadecyl acrylate(A16)and octadecyl acrylate(A18)were chosen as phase change materials.In the end,a series of cellulose-based solid-solid phase change materials(SSPCMs)and cellulose-based phase change fibers(PCFs)with thermally induced flexibility were synthesized through free radical polymerization,atom transfer radical polymerization(ATRP)and photoinduced metal-free surface initiated-ATRP(PMFSI-ATRP)by grafting comb-like poly(n-alkyl acrylate)(PAn,n=14,16 and 18).Moreover,the modified of graphene(GN16)was used as reinforced material,and its effect on the thermal performances of cellulose-based SSPCMs was investigated in detail.The main research contents are summarized as follows:(1)Cellulose acrylate(CA)was synthesized by grafting acryloyl chloride under homogeneous conditions,and the optimal grafting condition was studied.Then,CA-g-PAn(n=14,16 and 18)SSPCMs were furter prepared by grafting A14,A16 and A18 on the matrix of CA by free radical polymerization.Under the optimum reaction conditions,the thermal enthalpy(?H_m)of CA-g-PAn(n=14,16 and 18)is 62 J/g,76 J/g and 73 J/g,respectively.(2)Cellulose 2-bromopropionate(Cell-Br)as an initiator was prepared by using2-bromopropionate bromide.Then,A14 and A18 were grafted to Cell-Br by ATRP to prepare Cell-g-PAn(n=14 and 18)SSPCMs.Finally,the temperature range of the phase change was adjusted by changing the feed ration of A14 and A18.(3)A novel form-stable and thermally induced flexible cellulose/GN16 composite PCMs(CPm G-x)was successfully prepared.Here,PA16 as a phase change working substance was grafted to the supporting material cellulose by ATRP,and GN16 was used as an additive to enhance the enthalpy and the thermal conductivity.Due to the good dispersion and synergistic effect of GN16,its enthalpy value can be up to 103 J/g(5 wt.%,GN16),and the thermal conductivity can be improved to 1.32 W/m K(9 wt.%,GN16).Moreover,CPm G-x showed good thermal flexibility by triggering the phase transition of PA16.(4)A facile,environmental and low-cost strategy of PMFSI-ATRP was adopted to fabricate a multifunctional cellulose-based PCFs,which is composed of cellulosic fiber as supporting materials and PA16 used as phase change working substance.Through UV irradiation,PA16 was covalently grafted to the surface.As a result,a kind of modified cellulose-based PCFs with“core-shell”like structure was formed as expected,which has the thermal enthalpy up to 73 J/g and excellent superhydrophobic property.Moreover,it is dispensed with the processes of cellulose dissolving and spinning,which is benefit for scale-up and industrialization of cellulose based PCFs. |
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