Facile synthetic route toward poly(vinyl benzyl amine) and its versatile intermediates

Poly(vinyl benzyl amine) (PVBAm) has been synthesized by modifying poly(vinyl benzyl chloride) (PVBC) via an unique synthetic route. According to the literature, most polyamines are synthesized from PVBC through the Gabriel reaction. In this investigation, we adopt Staudinger synthesis to avoid drastic decomposition which occurs in the Gabriel reaction during synthesis. Three types of polyamine polymers - homopolymer, block copolymer and random copolymer, were synthesized without incurring any crosslinking reaction. The amine-containing polymers can further undergo ring-opening addition reaction with N-phenyl-3,3-dimethyl-azetidine-2,4-dione. Notably, the intermediates, phosphine imine and azide functionalities can be easily converted into various functionalities such as carbodiimide, imine, amine, triazo, aziridine, etc. by adding suitable reagents.     

TEMPO催化醇氧化反应进展

选择性催化氧化醇类化合物为相应的醛或酮是一类重要的官能团转化反应.四甲基哌啶氧化物(TEMPO)是一种含有稳定的氮氧自由基(NO·)的有机小分子催化剂,NO·可通过自身的强选择性,在加快醛或酮转化的同时不会过氧化成为羧酸.本文阐述了TEMPO催化体系催化醇选择性氧化反应的机理,在此基础上详述了过渡金属/TEMPO、非过...     

Hierarchical Assembly of Nanocellulose‐Based Filaments by Interfacial Complexation

In the present study, interfacial complexation spinning of oppositely charged cellulose‐materials is applied to fabricate hierarchical and continuous nanocellulose based filaments under aqueous conditions by using cationic cellulose nanocrystals with different anionic celluloses including soluble sodium carboxymethyl cellulose and insoluble 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy radical‐oxidized cellulose nanofibers and dicarboxylated cellulose nanocrystals (DC‐CNC). The morphologies of the wet and dry nanocellulose based filaments are further investigated by optical and electron microscopy. All fabricated continuous nanocellulose based filaments display a hierarchical structure similar to the natural cellulose fibers in plant cells. As far as it is known, this is not only the first report about the fabrication of nanocellulose based filaments by interfacial complexation of cationic CNCs with anionic celluloses but also the first demonstration of fabricating continuous fibers directly from oppositely charged nanoparticles by interfacial nanoparticle complexation (INC). This INC approach may provide a new route to design continuous filaments from many other oppositely charged nanoparticles with tailored characteristics.     

Cellulose nanofibers produced from various agricultural residues and their reinforcement effects in polymer nanocomposites

Cellulose nanofibers (CNFs) have gained widespread attention due to their extraordinary potential as superior reinforcement to improve physical and mechanical properties of polymer matrix nanocomposites. Biomass residues from local North Dakota represent a potential source for these high value structural constituents. Two types of soybean hull, wheat straw, and softwood flour were subjected to chemical pretreatments followed by mechanical fibrillation to produce CNFs. Atomic force microscopy and scanning electron microscopy results show that nanofibers with uniform diameters in the nanometer range can be easily synthesized. The nanofibers reinforcement potential was then explored via integration of the fibers into a poly(ethylene oxide) polymer matrix. Significant reinforcement effect of the nanofibers was observed from the nanocomposites: tensile modulus and yield strength of the nanocomposites were increased up to 154% and 103%, respectively. The CNFs extracted from the two types of soybean hull and wood flour showed stronger reinforcement (in terms of both modulus and yield strength) than that of the traditional wood pulp based CNFs. The nanofibers extracted from wheat straw showed higher strength but lower modulus compared with those of the traditional CNFs. More work is however needed to improve production reliability/repeatability of the agricultural residue based nanofibers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46304.     

4-羟基-2,2,6,6-四甲基哌啶氮氧自由基的制备

阐述了一种新的氧化方法，即在二价金属盐－过氧化氢（30％）氧化体系中，氧化4－羟基－2，2，6，6－四甲基哌啶醇成4－羟基－2，2，6，6－四甲基哌啶氮氧自由基，在70摄氏度下反应10h，产率95％以上。     

负载型TEMPO催化剂研究进展

在均相催化体系中,小分子TEMPO是醇选择性氧化为相应醛和酮最重要的有机催化剂之一,但因价格昂贵且回收工艺复杂等因素限制了均相TEMPO催化剂的大规模应用。负载型TEMPO催化剂因在两相体系中易与产物分离实现回收再利用而备受关注。TEMPO催化剂的固载化处理有效实现TEMPO的回收再利用,经多次重复使用仍保持较高的催化活性,且催化剂载体的特性赋予其比均相催化更高的催化活性。根据载体不同,分别介绍固体颗粒负载型TEMPO催化剂(包括无机颗粒和有机非溶性聚合物颗粒)和可溶性聚合物负载型TEMPO催化剂应用于醇氧化的研究进展,并评价两类负载型TEMPO催化剂的优缺点,对负载型TEMPO催化剂的发展前景进行展望。     

基于分子修饰C-COS的高吸湿保湿机理

采用漆酶/2,2,6,6-四甲基哌啶-1-氧自由基(TEMPO)体系氧化壳寡糖制备了一种高吸湿保湿性羧基化壳寡糖(C-COS)。利用低场核磁共振(LF-NMR)、FTIR和13CNMR考察了其分子间氢键的变化并进一步推测出吸湿保湿机理。结果表明:在C-COS的吸湿过程中,聚合物分子与水之间存在着分子间氢键作用力。C-COS分子上极性较强的羧酸根产生了新的氢键效应,结合升温红外中3363、1643 cm~(–1)处吸收峰强度的减小和同样波数下吸收峰频率的蓝移以及溶胀红外中1643cm~(–1)处吸收峰强度的增加,确定了C-COS分子中羧酸根与水之间所形成的水合氢键(H—O—H···O—C==O)。另外,C-COS的保湿机理在于聚合物溶解在水体系中能够形成一种巨大的聚合物-水网状结构,促使水分子以氢键的形式被牢牢地锁住在这种网状结构中。     

蔗渣大分子半纤维素和纳米纤维素的一体式全制备

使用质量分数4%~20%的NaOH溶液预处理蔗渣,以33.5%~73.1%的较高得率获得了平均分子质量为40~60 kDa的大分子半纤维素,然后采用2,2,6,6-四甲基哌啶-1-氧自由基（TEMPO）氧化法,在没有额外机械力作用下,将抽提后的残渣成功转化成直径小于15 nm、长度几十纳米至2 μm且分散性很好的TEMPO氧化纤维素纳米晶体（TOCN）。研究还发现,NaOH预处理不但可以有效地从蔗渣中提取半纤维素,而且明显提高了TEMPO氧化法制备纳米纤维素的效率。传统TEMPO氧化纤维原料需机械处理且只能制备CNF,而本研究通过NaOH预处理协同TEMPO氧化法,无需机械处理即可得到具有较好尺寸的CNC。另外,预处理所用碱浓的增加导致纤维素的晶型发生转变,且随着预处理时间的延长,其发生转变时所需的碱浓降低。     

Effect of oat β‐glucan and its oxidised derivative on the quality characteristics of sponge cake

The objective of this study was to investigate the characteristics of sponge cakes containing native oat β‐glucan (BG‐B) and its oxidised derivative with TEMPO (2, 2, 6, 6‐tetramethyl‐1‐piperidine oxoammonium ion) (Oxi‐B). BG‐B and Oxi‐B were substituted at 1% (w/w) into a formulation, and then the effects of BG‐B and Oxi‐B addition on the pasting properties of wheat flour and the physicochemical and textural properties of sponge cakes were determined. The pasting parameters of wheat flour were increased by BG‐B, whereas they were decreased in wheat flour with added Oxi‐B. The cake containing Oxi‐B had a lower volume, and a higher symmetry and uniformity than the BG‐B cake. The Oxi‐B cake exhibited smaller L* and b* values and a higher a* value than the control in crumb and crust colour. According to texture profile analysis, the BG‐B cake had increased hardness, chewiness and gumminess, whereas the Oxi‐B cake had decreased hardness.