2,2,6,6-四甲基-4-甲氧基哌啶氮氧自由基制备方法的改进

阐述了一种制备 4 -甲氧基 -2 ,2 ,6 ,6 -四甲基哌啶氮氧自由基的改进方法 :以四氢呋喃为溶剂 ,0℃时 ,在N2 的保护下和NaH的存在下 ,2 ,2 ,6 ,6 -四甲基 -4 -羟基哌啶氮氧自由基与MeI在室温反应 5h。分离混合物 ,得到粘稠状红色液体 ,加入正己烷 ,在 -2 0℃条件下储存 ,结晶出针状深红色的晶体。熔点 :4 2～ 4 3℃ ,产率 70 %以上     

TEMPO/NaBr/NaClO体系氧化玉米淀粉的研究

针对以2,2,6,6-四甲基哌啶-1-氧基自由基（TEMPO）-NaClO-NaBr为代表的亚硝酰自由基选择性氧化体系,本文以玉米淀粉为原料,NaClO为氧化剂,TEMPO和NaBr为催化剂,制备了氧化玉米淀粉.在不糊化的前提下,以5 g淀粉为原料,研究了在pH为10.00,反应温度为20℃,反应时间为2.5h的条件下,不同氧化剂用量对氧化淀粉羧基质量分数的影响,通过红外光谱（IR）对氧化玉米淀粉的结构进行表征,研究结果表明,当NaClO用量为67.5 mL时,氧化淀粉的羧基质量分数可达10.60％.该研究为TEMPO/NaBr/NaClO体系氧化淀粉提供了理论参考.     

Polystyrene composites of single‐walled carbon nanotubes‐graft‐polystyrene

Single‐walled carbon nanotubes (SWCNTs) dispersed in N‐methylpyrrolidone (NMP) were functionalized by addition of polystyryl radicals from 2,2,6,6‐tetramethyl‐1‐piperidinyloxy‐ended polystyrene (SWCNT‐g‐PS). The amount of polystyrene grafted to the nanotubes was in the range 20‐25 wt% irrespective of polystyrene number‐average molecular weight ranging from 2270 to 49 500 g mol^?1. In Raman spectra the ratios of D‐band to G‐band intensity were similar for all of the polystyrene‐grafted samples and for the starting SWCNTs. Numerous near‐infrared electronic transitions of the SWCNTs were retained after polymer grafting. Transmission electron microscopy images showed bundles of SWCNT‐g‐PS of various diameters with some of the polystyrene clumped on the bundle surfaces. Composites of SWCNT‐g‐PS in a commercial‐grade polystyrene were prepared by precipitation of mixtures of the components from NMP into water, i.e. the coagulation method of preparation. Electrical conductivities of the composites were about 10^?15 S cm^?1 and showed no percolation threshold with increasing SWCNT content. The glass transition temperature (T_g) of the composites increased at low filler loadings and remained constant with further nanotube addition irrespective of the length and number of grafted polystyrene chains. The change of heat capacity (ΔC_p) at T_g decreased with increasing amount of SWCNT‐g‐PS of 2850 g mol^?1, but ΔC_p changed very little with the amount of SWCNT‐g‐PS of higher molecular weight. The expected monotonic decrease in ΔC_p coupled with the plateau behavior of T_g suggests there is a limit to the amount that T_g of the matrix polymer can increase with increasing amount of nanotube filler. Copyright © 2012 Society of Chemical Industry     

木素对TEMPO氧化竹浆制备纳米纤维素的影响

以卡伯值不同的2种未漂硫酸盐竹浆(卡伯值为25.5和11.7的竹浆分别标记为SHK和SLK)为原料,通过TEMPO/NaBr/NaClO体系氧化及高压均质处理,制备了TEMPO氧化纳米纤维素(TOCN),并利用抽滤法制备TOCN膜。系统地研究了2种竹浆的TEMPO氧化过程、TEMPO氧化浆性能、TOCN性能及TOCN膜的力学性能等,探讨了木素对竹浆TEMPO氧化过程和TOCN制备的影响。结果表明,SHK的TEMPO氧化速率高于SLK,但SLK-TEMPO氧化浆的羧基含量达到1.01 mmol/g,高于SHK-TEMPO氧化浆的羧基含量(0.89 mmol/g)。2种TOCN形态结构差异不大,均呈纤丝状结构,直径约为5～8 nm,长径比>100,且均保持纤维素I的晶型结构;SLK-TOCN的结晶度和悬浮液的透光度均略高于SHK-TOCN。2种TOCN膜均具有优良的光学性能和力学性能,SLK-TOCN膜的杨氏模量、拉伸强度及裂断伸长率分别为2.6 GPa、92 MPa和10.9%,均高于SHK-TOCN膜的2.4 GPa、90 MPa和8.7%。     

玉米秸秆糠醛剩余物纳米纤维素薄膜的制备与表征

本研究通过硫酸水解、超声和TEMPO (2,2,6,6-四甲基哌啶氧化物)氧化3种处理方法分别制备了纳米纤维素（CFR-CNC、CFR-CNF和CFR-TNC）及相应薄膜,对纳米纤维素微观形态、结晶度、热稳定性和化学结构进行了表征,同时比较了纳米纤维素薄膜的形态和机械性能。结果表明,3种纳米纤维素具有不同的长宽比（29.2、163.7、132.2）和结晶度（62.5%、52.8%、43.9%）。红外光谱图表明,3种纳米纤维素的纤维素分子结构并未改变,且CFR-TNC成功引入羧基。3种纳米纤维素薄膜中,CFR-CNF薄膜具有较高的拉伸强度（36.6 MPa）,CFR-CNC薄膜具有较好的抗形变能力,并且3种薄膜均具有良好的透光性。     

TEMPO氧化纳米纤维素的制备及其对纸张性能的影响

以漂白桉木浆和废报纸为原料,利用2,2,6,6-四甲基哌啶-1-氧自由基(TEMPO)/NaBr/NaClO氧化体系对其进行处理制备氧化纳米纤维素,并探究两种氧化纳米纤维素添加量对纸张性能的影响。研究结果表明:桉木浆氧化纳米纤维素的平均纤维长度约为75~95 nm,长径比约为6.5~8.5,均高于废报纸氧化纳米纤维素(45~75 nm,4~6)。添加桉木浆氧化纳米纤维素和废报纸氧化纳米纤维素均可使纸张抗张指数、耐破指数和撕裂指数增加。添加6%桉木浆氧化纳米纤维素时,纸张抗张指数由21.16(N·m)/g增加至31.37(N·m)/g,耐破指数由1.32(kPa·m^(2))/g增加至1.84(kPa·m^(2))/g,撕裂指数由6.61(mN·m^(2))/g增加至8.03(mN·m^(2))/g;添加6%废报纸氧化纳米纤维素时,纸张抗张指数由21.16(N·m)/g增加至27.22(N·m)/g,耐破指数由1.32(kPa·m^(2))/g增加至1.79(kPa·m^(2))/g,添加4%废报纸氧化纳米纤维素,纸张撕裂指数由6.61(mN·m^(2))/g增加至8.12(mN·m^(2))/g,可见,添加桉木浆氧化纳米纤维素效果更佳。添加1%阳离子淀粉,有助于两种氧化纳米纤维素对纸张强度的提高,其中桉木浆氧化纳米纤维素可使抗张指数最大提高51.09%,耐破指数提高50.00%,撕裂指数提高27.62%。     

苯甲醇液相氧化合成苯甲醛的连续流工艺

在液相条件下以苯甲醇为原料,次氯酸钠溶液为氧化剂,2,2,6,6-四甲基哌啶-1-氧自由基（TEMPO）为氧化催化剂,在连续流微通道反应器中液相氧化合成苯甲醛。考察了苯甲醇与次氯酸钠溶液的物质的量配比、催化剂用量、反应温度、溶剂以及停留时间对苯甲醛合成的影响,并进行了工艺优化。结果表明：当次氯酸钠与苯甲醇的物质的量比为1.25∶1、苯甲醇与TEMPO的物质的量比为1∶0.01、苯甲醇与DMF的体积比为1∶10、 pH=8、反应温度为0℃、停留时间为10min时,苯甲醛的收率可达95.1%。     

NaOH/硫脲/尿素预处理对棉纤维TEMPO选择性氧化的影响

采用NaOH/硫脲/尿素体系对棉纤维进行预处理,再进行选择性氧化,可以有效提高氧化棉纤维的羧基生成量。对比研究预处理棉纤维与普通棉纤维经2,2,6,6-四甲基哌啶氮氧自由基(TEMPO)选择性氧化后的羧基含量、纤维形态以及黏度。结果表明,经NaOH/硫脲/尿素体系预处理能够加快氧化反应速率,增加羧基生成量,但对纤维有一定的损伤。其中,羧基生成量随着纤维质量分数的增加呈先增加后减少的趋势,当纤维素质量分数为6%时,羧基生成量最大,棉纤维的可及度和反应性提高。纤维形态分析表明,经NaOH/硫脲/尿素体系预处理的棉纤维润胀溶解程度要大于未预处理的氧化棉纤维;在TEMPO的氧化条件下,氧化棉纤维的相对黏度随着纤维素质量分数增加而增加;当纤维素质量分数较高时,氧化过程中氧化棉纤维的羧基生成量和降解程度都近似于原纤维。     

TEMPO促成的瓜尔胶及羟丙基瓜尔胶的选择性氧化

2,2,6,6-四甲基哌啶氧化物自由基(TEMPO)-NaClO-NaBr是一种新的具有很高选择性的氧化体系。文章研究了该体系在pH 9.30和体系温度为0℃时对瓜尔胶的氧化机理。用IR和13C-NMR表征了瓜尔胶及羟丙基瓜尔胶在氧化后的结构变化,证实了经氧化后(羟丙基)瓜尔胶结构中C6上伯醇可被选择性转化为羧基;另外在本实验条件下,随着瓜尔胶羟丙基取代度的增加,其氧化程度也增加。     

Interpolymer radical coupling: A toolbox complementary to controlled radical polymerization

The current review focuses on the relevance and practical benefit of interpolymer radical coupling methods. The latter are developing rapidly and constitute a perfectly complementary macromolecular engineering toolbox to the controlled radical polymerization techniques (CRP). Indeed, all structures formed by CRP are likely to be prone to radical coupling reactions, which multiply the available synthetic possibilities. Basically, the coupling systems can be divided in two main categories. The first one, including the atom transfer radical coupling (ATRC), silane radical atom abstraction (SRAA) and cobalt-mediated radical coupling (CMRC), relies on the recombination of macroradicals produced from a dormant species. The second one, including atom transfer nitroxide radical coupling (ATNRC), single electron transfer nitroxide radical coupling (SETNRC), enhanced spin capturing polymerization (ESCP) and nitrone/nitroso mediated radical coupling (NMRC), makes use of a radical scavenger in order to promote the conjugation of the polymer chains. More than a compilation of macromolecular engineering achievements, the present review additionally aims to emphasize the particularities, synthetic potential and present limitations of each system.