Synthesis And Performance Of Solar Thermal Conversion Form-Stable Phase Change Materials With Polyether Structure

The visible light accounts for approximately40%of solar radiation, which almost cannot be directly or effectively applied by phase change materials due to low thermal efficiency. In the present thesis, in view of this scientific issue, novel organic photothermal conversion materials were designed and synthesized based on colorants and phase change materials. The colorants (dyes and carbon) in the photothermal conversion materials were used as a photon antenna that served as an effective "photon capturer and molecular heater" of light-to-heat conversion, and the phase change material stored heat energy by a phase transition with high energy storage density. The novel materials have some notable advantages, such as UV-Vis sunlight-harvesting, light-thermal conversion and thermal energy storage for the realization of the highly efficient utilization of solar radiation.In this thesis, epoxy group or an isocyanate group was introduced to the terminal hydroxyl group of polyether (polyethylene glycol monomethyl ether or polyethylene glycol) by chemical modification that obtained reactive polyether; the colorant was designed and synthesized or surface-modified by using the diazotization-coupling, chlorosulfonated condensation or radical reaction to obtain the colorant with reactive or excellent dispersion in organic solvents. Then the light-thermal conversion organic shape-stabilized phase-change materials were designed and synthesized by chemical bond, which mainly contained cross-linking shape-stabilized materials, polycondensation polymer shape-stabilized materials and carbon/phase change material (PCM) composites. These photothermal conversion materials were characterized by UV-Vis, FT-IR,’H-NMR and13C-NMR.Firstly, the reactive MPEG and the reactive dyes were grafted onto polyethylene polyamine to obtain the organic photothermal conversion solid-liquid phase change engergy storage materials with the remaining amine gruops. Using toluene-2,4-diisocyanate (TDI) and cyanuric chloride as crosslingking agents, the remaining reactive amino groups of the solid-liquid phase change engergy storage materials were cross-linked, and the cross-lingking shape-stabilized phase change materials were obtained. The materials have some notable advantages, such as shape-stabilized properties in phase change process and strong rigidity. Simultaneously, the materials have a high photothermal conversion and energy storage efficiency (single band,η>0.94; visible light400-700nm,η>0.74) and high energy storage density (△H>100J/g).Secondly, the dyes containing two reactive groups (hydroxyl or amino group) and PEG were conducted by TDI through a two-step polymerization process. Then, the linear polycondensation photothermal conversion materials were obtained, and the materials exhibited high strength and flexibility. Simultaneously, the materials have a high photothermal conversion and energy storage efficiency (single band, η>0.90; visible light400～700nm, η>0.76), high energy storage density (△Hmax=142.9J/g) and hape-stabilized phase change energy storage and so on.Finally, the surfaces of carbon materials (carbon black, multi-walled carbon nanotubes and single-walled carbon nanotubes) were modified by reacting them with4-nitrophenyldiazonium cations to obtain a uniform dispersion in organic solvents. The surface-modified carbon was successfully hybridized by using ultrasound in PCM, thereby obtaining novel carbon/PCM composites. The materials have some notable advantages, such as a full band absorption of sunlight (400～700nm, η>0.84), a high thermal conductivity as compared to pure organic materials (content of2%, the material thermal efficiency is improved by25.1%); Additionally, a preliminary study showed that carbon/PCM composites exhibited high strength and flexibility.