本文選題：TEMPO氧化體系　切入點：膽甾型液晶　出處：《青島科技大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：基于可再生資源的納米材料因其廣闊的應(yīng)用前景而引起了人們越來越多的興趣,天然納米材料所具有的生態(tài)優(yōu)勢、加工性能和光子晶體特性,對于多功能納米材料的發(fā)展意義重大。纖維素是一類來源十分廣泛的可持續(xù)發(fā)展材料,通過改性處理得到的納米纖維素可以用于各種新型材料的制備。2,2,6,6-四甲基哌啶-1-氧自由基(2,2,6,6-tetramethylpiperidine-1-oxyl radical,TEMPO)-NaBr-NaClO催化氧化體系是一種對纖維素進(jìn)行氧化改性制備纖維素納米晶體(cellulose nanocrystals,CNCs)的有效方法,在溫和的反應(yīng)條件下,可以有效地選擇性氧化CNCs表面C6位伯羥基為羧基,實現(xiàn)對其表面的功能化。本論文中,采用鹽酸水解和TEMPO體系氧化的方法處理棉花纖維素,制備了TEMPO體系氧化后的棉花纖維素納米晶體(TEMPO-oxidized cotton cellulose nanocrystals,c-TOCNs)及其溶致膽甾型液晶(chiral nematic liquid crystals,N*-LCs)。通過調(diào)節(jié)c-TOCNs懸浮液的濃度,利用偏光顯微鏡技術(shù)(polarizing optical microscopy,POM)系統(tǒng)地研究了其形成液晶(liquid crystals,LCs)的臨界濃度。研究結(jié)果表明,c-TOCNs懸浮液形成LCs的臨界濃度是4.1 wt%,并首次成功地在9.0 wt%的濃度下觀察到了N*-LCs的特征結(jié)構(gòu)指紋織構(gòu)。與此同時,將TEMPO氧化體系得到的溶致N*-LCs的液晶行為與硫酸水解體系進(jìn)行了對比,并討論了納米晶體尺寸和表面電荷密度這兩個因素對LCs形成的臨界濃度和螺距(helical pitch,P)大小的影響。通過向c-TOCNs懸浮液中添加不同濃度NaCl溶液以改變其離子強(qiáng)度的方法,探究了離子強(qiáng)度對羧基化纖維素溶致N*-LCs液晶行為的影響。研究結(jié)果表明隨著懸浮液中NaCl濃度的增大,各項異性相中有序疇的范圍變少,且P減小。這是由于NaCl的加入對c-TOCNs的表面電荷產(chǎn)生了屏蔽作用,導(dǎo)致雙電層厚度減小,帶電納米棒的有效直徑和表觀體積下降,使得c-TOCNs間的靜電排斥作用減弱,從而減小了P。聚苯胺(polyaniline,PANI)具有優(yōu)異的導(dǎo)電性能,將其與纖維素復(fù)合可以制備新型導(dǎo)電納米復(fù)合材料。本論文中,從海鞘中提取出纖維素,并通過TEMPO體系氧化法制備了海鞘纖維素納米晶體(TEMPO-oxidized tunicate cellulose nanocrystals,t-TOCNs)。然后以t-TOCNs為模板,利用原位聚合法,成功地制備了PANI/t-TOCNs復(fù)合材料。羧酸根的引入很好地提高了t-TOCNs的分散性,并且提供了較多的氫鍵位點,這些氫鍵位點吸引苯胺單體生長,從而形成導(dǎo)電涂覆。PANI和t-TOCNs之間主要是通過氫鍵作用結(jié)合在一起,PANI的加工性能得到了較好改善。制備的PANI/t-TOCNs復(fù)合材料具有良好的導(dǎo)電性,電導(dǎo)率可以達(dá)到0.26 S·cm-1,表現(xiàn)出半導(dǎo)體的性質(zhì),隨著An/OH的比例增大,導(dǎo)電性增強(qiáng),將在超級電容器、傳感器等領(lǐng)域有廣闊應(yīng)用。
[Abstract]:Nanomaterials based on renewable resources have attracted more and more interest due to their wide application prospects. Natural nanomaterials have ecological advantages, processing properties and photonic crystal properties. For the development of multifunctional nanomaterials. Cellulose is a class of sustainable development materials from a wide range of sources. The modified nano-cellulose can be used in the preparation of various new materials. The catalytic oxidation system of 6-tetramethylpiperidine-1-oxyl radical TEMPO- NaBr-NaClO is an effective method for the preparation of cellulose nanocrystalline CNCsby oxidation modification. Under mild reaction conditions, the surface of CNCs can be effectively selectively oxidized by C _ 6 hydroxyl group as carboxyl group. In this paper, hydrochloric acid hydrolysis and TEMPO system oxidation were used to treat cotton cellulose. The cotton cellulose nanocrystalline (TEMPO-oxidized cotton cellulose nanocrystalsc TOCNs) and its lyotropic cholesteric liquid crystal, chiral nematic liquid crystalsn, were prepared by adjusting the concentration of c-TOCNs suspension. The critical concentration of liquid crystal crystals formed by polarizing optical microscopy (POM) has been systematically studied. The results show that the critical concentration of c TOCNs to form LCs is 4. 1 wtlong, and N- LCs have been successfully observed for the first time at a concentration of 9. 0 wt%. At the same time, The liquid crystal behavior of lysogenic Na-LCs obtained by TEMPO oxidation system was compared with that of sulfuric acid hydrolysis system. The effects of nanocrystalline size and surface charge density on the critical concentration of LCs formation and the size of helical pitch-P were discussed. The method of changing the ionic strength of c-TOCNs suspension by adding different concentrations of NaCl solution was discussed. The effect of ionic strength on the liquid crystalline behavior of Na-LCs induced by carboxylated cellulose was investigated. The results showed that the range of ordered domains in different heterosexual phases decreased with the increase of NaCl concentration in the suspension. The decrease of P is due to the shielding effect of NaCl on the surface charge of c-TOCNs, which results in the decrease of the thickness of double layer, the decrease of effective diameter and apparent volume of charged nanorods, and the weakening of electrostatic repulsion between c-TOCNs. Therefore, P.Polyaniline polyaniline (PANI) has excellent electrical conductivity. A new type of conductive nanocomposites can be prepared by combining it with cellulose. In this paper, cellulose was extracted from sea sheath. TEMPO system oxidation method was used to prepare tunicate cellulose nanocrystalst-TOCNs, and then PANI/t-TOCNs composites were prepared by in situ polymerization with t-TOCNs as template. The dispersity of t-TOCNs was improved by the introduction of carboxylic acid. And it provides a lot of hydrogen bonding sites that attract aniline monomers to grow. As a result, the processing properties of the conductive coating. Pani and t-TOCNs are mainly combined by hydrogen bonding. The prepared PANI/t-TOCNs composites have good electrical conductivity and the electrical conductivity can reach 0.26 S 路cm-1, which shows the properties of semiconductors. As the proportion of An/OH increases and conductivity increases, it will be widely used in supercapacitors, sensors and other fields.
【學(xué)位授予單位】：青島科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O636.11;TB332

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本文編號：1641630