【摘要】：纖維素從其儲(chǔ)量、力學(xué)性能、化學(xué)性能、生物相容性可再生特性上都無(wú)疑是制備環(huán)境友好和生物相容性材料的最佳天然高分子原料。利用纖維素制備多孔材料是目前纖維素的一個(gè)研究方向。以纖維素為基體的纖維素多孔材料能夠結(jié)合多孔材料的結(jié)構(gòu)特征和纖維素分子優(yōu)秀的理化性質(zhì)、環(huán)境友好特性和生物相容性,具有廣泛的應(yīng)用范圍和長(zhǎng)遠(yuǎn)的應(yīng)用前景。本文以N,N-二甲基乙酰胺(DMAc)為活化劑,研究了其對(duì)微晶纖維素的熱活化機(jī)理,使微晶纖維素能在常溫下溶解于LiCl/DMAc中。經(jīng)過(guò)溶膠凝膠和溶劑置換得到具有紫外線(xiàn)吸收效果的透明纖維素水凝膠。以此水凝膠為前驅(qū)體,經(jīng)超臨界干燥和二氧化碳干燥制備了結(jié)構(gòu)可控的纖維素多孔材料。并將所得多孔材料應(yīng)用于摻雜石墨微粉(粒徑d23μm)的PEG的封裝得到纖維素多孔材料封裝PEG的復(fù)合材料。通過(guò)X射線(xiàn)衍射(XRD)、傅里葉紅外光譜(FTIR)、掃描電鏡(SEM)觀(guān)察和差示掃描量熱(DSC)等對(duì)所制備的材料進(jìn)行表征。并對(duì)DMAc熱活化微晶纖維素機(jī)理,纖維素孔結(jié)構(gòu)的控制和形成機(jī)理,以及孔結(jié)構(gòu)對(duì)儲(chǔ)熱、導(dǎo)熱性能、形狀穩(wěn)定性的影響進(jìn)行了深入研究。研究表明:150℃加熱條件下,DMAc造成微晶纖維素晶體缺陷增加,使得LiCl/DMAc溶解體系對(duì)纖維素溶解的可及性增加,使微晶纖維素在常溫下就能溶解于LiCl/DMAc溶解體系。冷凍干燥前,預(yù)冷凍條件對(duì)纖維素多孔材料的孔結(jié)構(gòu)起決定作用:預(yù)冷凍條件決定了纖維素水凝膠內(nèi)冰晶的生長(zhǎng)及其尺寸、形狀、分布等,纖維素層片聚集于冰晶晶界上,冰晶升華后形成材料最終的孔結(jié)構(gòu)。因此,通過(guò)控制冰晶的生長(zhǎng)和結(jié)構(gòu)可實(shí)現(xiàn)對(duì)纖維素多孔材料結(jié)構(gòu)的控制,據(jù)此制備了具有取向結(jié)構(gòu)的纖維素多孔材料。纖維素多孔材料封裝PEG的復(fù)合材料的相變潛熱可達(dá)到93.68J·g-1,熱導(dǎo)率可達(dá)到3.09 W·K-1·m-1,具有作為相變儲(chǔ)熱材料應(yīng)用的巨大潛力。復(fù)合材料中纖維素層片越多越密集,材料內(nèi)部熱傳導(dǎo)熱阻增加,導(dǎo)熱性能下降,纖維素多孔材料的連通結(jié)構(gòu)和取向結(jié)構(gòu)有利于PEG填充,同時(shí)材料的導(dǎo)熱性能也較好。在加熱相變過(guò)程中,復(fù)合材料的相變潛熱低于所含PEG結(jié)晶潛熱總量,可能受到PEG和纖維素之間形成氫鍵的影響。通過(guò)本課題的研究工作完善了纖維素多孔材料的制備理論,探索了一種結(jié)構(gòu)和性能可控的制備方法,拓展了纖維素多孔材料的應(yīng)用范圍。
[Abstract]:Cellulose is undoubtedly the best natural polymer material for the preparation of environment-friendly and biocompatible materials in terms of its reserves, mechanical properties, chemical properties and biocompatibility and renewable properties. The preparation of porous materials from cellulose is a research direction of cellulose at present. Cellulosic porous materials based on cellulose can combine the structural characteristics of porous materials with excellent physical and chemical properties of cellulose molecules, environment-friendly properties and biocompatibility, so it has a wide range of applications and long-term application prospects. In this paper, the thermal activation mechanism of N- dimethyl acetamide (DMAc) on microcrystalline cellulose has been studied. The microcrystalline cellulose can be dissolved in LiCl/DMAc at room temperature. Transparent cellulose hydrogel with UV absorption effect was obtained by sol-gel and solvent replacement. Cellulose porous materials with controllable structure were prepared by supercritical drying and carbon dioxide drying. The porous materials were used in the encapsulation of PEG doped with graphite powder (d23 渭 m) to obtain the composite material of PEG encapsulated by cellulose porous materials. The prepared materials were characterized by X-ray diffraction (XRD) (XRD), Fourier transform infrared spectroscopy (XRD),) (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The mechanism of thermal activation of microcrystalline cellulose by DMAc, the control and formation of cellulosic pore structure, and the effects of pore structure on heat storage, thermal conductivity and shape stability were also studied. The results show that under the heating temperature of 150 鈩，

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