Synthesis Of Functionalized Polymers And Their Applications In Thermal Energy Storage

With the fast pace of industrialization and the rapid explosion of word population,global energy crisis and environmental contamination are day by day serious.Organic phase change materials(PCMs)have drawn tremendous attention and have been proved as one of the most promising candidate materials for overcoming the energy crisis and environmental pollution because of their ability to charge or discharge large quantities of latent heat reversibly with small temperature fluctuations during the phase transition processes.However,the liquid leakages and poor thermal conductivity of PCMs during liquidation and solidification have significantly impeded their practical applications in thermal energy storage.The most effective strategy to overcome these drawbacks is a form-stabilization technique which involves imprisoning PCMs in supporting networks.Form-stable PCMs(FSPCMs)can be fabricated by confining PCMs within polymer-based materials with a network structure,such as polyacrylate,polyolefins,styrenic block copolymers,polyurethane,and biopolymers.Herein,the purpose of the work is based on elaborate molecular design,delivering a novel shape-stabilization strategy to fabricate a series of new FSPCMs by employing comb-like polynorbomenes or precisely diphenyl ether-functionalized polyethylene as the supporting networks and PCMs as the latent heat materials.The main work is shown below:1.A series of novel polynorbornenes with different length of the n-alkyl side chains were designed and successfully synthesized via ring-opening metathesis polymerization.Molecular chain structures of all the monomers and polymers were meticulously investigated by1H NMR and 13C NMR spectroscopy.TGA analysis indicated that all the polymers possessed excellent thermal stabilities and the existence of two-stage decompositions.On the other hand,DSC measurements suggested that the phase transition behavior of these polymers is strongly dependent on the length of the n-alkyl side chains.When the number of carbon atoms in the n-alkyl side chains was 16 or higher,not only was an endothermic peak at high temperature observed,but n-alkyl side chain crystallization was also detected;otherwise,only an endothermic peak at around 153? was observed.2.We provide a novel shape-stabilization strategy to fabricate a series of form-stable PCMs(FSPCMs)by employing comb-like polynorbornenes along with the octadecylamine-functionalized graphene(GNS-ODA)nanosheets as the supporting networks and paraffin as the latent heat material.The octadecyl chain incorporated on the surface graphene not only prevented from the graphene aggregation,but also endowed excellent structural stability to the FSPCMs.Meanwhile,the toughness of the FSPCMs was further improved with the addition of the comb-like polynorbornenes Paraffin was tightly imprisoned in the frameworks formed by the GNS-ODA nanosheets and comb-like polynorbornenes,resulting in no leakage even above their melting temperature.The multiple thermal cycling tests proved that these FSPCMs had excellent thermal cycling reliability.In particular,they were also capable of absorbing or releasing thermal energy at a high rate,offering a significant potential to be used as the effective thermal management materials.Notably,comb-like polynorbornenes demonstrated to be capable of being employed as the supporting networks of paraffin,opening a new door for fabricating novel types of FSPCMs as well as broadening the practical application of the comb-like polymers.3.In order to further enrich the breeds of polymer matrix framework-based PCMs,we synthesized a new class of the comb-like polynorbomenes with the branched alkyl side chain,annotated as PNb(10,12)C,via ring-opening metathesis polymerization(ROMP).And then,we prepared a series of novel FSPCMs using the comb-like polynorbornenes with the branched alkyl side chain along with 3D flower-like MoS2 nanospheres acted as the supporting materials and n-octadecanol(OCC)as the latent heat material.3D flower-like MoS2 nanospheres not only facilitated thermal conductivity but also endowed excellent structural stability to the FSPCMs.OCC was tightly confined in the frameworks formed by PNb(10,12)C and the 3D flower-like MoS2 nanospheres,resulting in no leakage even above their melting temperature.As expected,the FSPCMs demonstrated reliable thermal stability and high thermal energy storage capacity.In particular,they were capable of absorbing or releasing stored thermal energy at a high rate,illustrating a great potential to be used as the effective thermal energy storage and thermal management systems.4.We demonstrated the facile synthesis of a new class of functionalized polyethylene containing precisely sequenced diphenyl ether moieties via acyclic diene metathesis(ADMET)polymerization of a series of ?,?-diene monomers with central diphenyl ether segments and subsequent exhaustive hydrogenation.1H.NMR and 13C NMR spectroscopy have provided unambiguous evidence for precise primary architectures of the prepared monomers and the resulting polymers.The thermal stability of all polymers was systematically investigated by thermogravimetric analysis(TGA),indicating the introduction of diphenyl ether segments significantly enhanced the thermal stability of the polyethylene.DSC results indicated that only HPM3 manifested semi-crystallinity with Tm of 61.8? while HPM1 and HPM2 were fully amorphous polymers.On the other hand,ROIMP not only disorganized the regular order of homopolymers,but also decreased the amount of diphenyl ether segments and extends the methylene unit lengths in the saturated copolymers,resulting in all those saturated irregularly sequenced copolymers showed a broad and weak melting transition.