N-异丙基丙烯酰胺/N-羟甲基丙烯酰胺共聚物及其水凝胶的合成及其温敏性研究

通过自由基聚合合成了N-异丙基丙烯酰胺(NIPAm)与N-羟甲基丙烯酰胺(NHMPA)的共聚物及其水凝胶。研究发现，调节两单体的配比可得到不同的低临界溶液温度(LCST)值的共聚物及水凝胶。结果表明，NHMPA的加入不改变PNIPAm的温敏性，但可有效的调节其LCST值。     

疏水基改性聚丙烯酰胺的合成及溶液性质

利用自由基胶束聚合法,由丙烯酰胺和甲基丙烯酸十八酯共聚合成了疏水缔合型水溶性聚合物.通过红外光谱表征了共聚物的结构,考察了共聚物浓度、盐浓度、剪切速率以及温度对共聚物溶液性能的影响.试验结果表明,聚合物质量分数大于临界缔合浓度(2%)时,溶液的粘度急剧增大;疏水缔合聚合物溶液的表观粘度随着溶液中NaCl质量分数的增加而增大.     

疏水缔合水溶性聚合物AO的溶液粘度行为研究

研究了稀溶液中疏水链链长、无机电解质NaCl和CaCl2对疏水缔合水溶性丙烯酰胺／甲基丙烯酰氨乙基-二甲基烷基溴化铵／丙烯酸钠共聚物(AO)在水溶液中的特性粘数和Huggins常数的影响，以及聚合物AO-8的特性粘数和Huggins常数随温度的变化。结果表明：在稀溶液中，无机电解质离子强度增大，共聚物AO在NaCl和CaCl2溶液中的特性粘数减小，Huggins常数增大。在亚浓溶液范围对聚合物质量分数、温度、剪切速率及NaCl含量对聚合物的水溶液表现粘度的影响进行了研究，观察到疏水缔合聚合物盐水溶液在NaCl含量提高的情况下，出现的增粘现象。     

ATRP技术制备末端和中间功能化的温度敏感性聚N,N-二乙基丙烯酰胺

合成了2种含有二硫吡啶结构的原子转移自由基聚合(ATRP)引发剂,ATRP引发剂结构采用核磁共振氢谱(1H-NMR)表征.结果显示,二硫吡啶结构被成功引入引发剂结构末端或链中间.利用2种ATRP引发剂分别制备了链末端功能化和链中间功能化的聚N,N-二乙基丙烯酰胺(pDEAAm).采用1H-NMR和凝胶渗透色谱(GPC)对聚合物结构和分子量进行了表征.1H-NMR结果显示,二硫吡啶基团被引入聚合物链末端或中间.GPC结果表明,末端功能化和中间功能化的聚N,N-二乙基丙烯酰胺(pDEAAm)分子量分布指数分别为1.21和1.23,实现了分子量的可控聚合.并且,具有2个引发位点的引发剂引发单体得到聚合物的分子量较大.采用紫外-可见分光光度法研究了聚合物在溶液中的温度响应性.紫外-可见分光光度法结果说明,pDEAAm溶液在28°C发生相分离,在溶液中表现出温度响应性,且最低临界溶解温度(LCST)为28°C.在末端功能化和中间功能化温敏型pDEAAm可用于嵌段共聚物的合成以及与生物大分子的定位结合.特别对于中间功能化的pDEAAm,有望用于星型聚合物和多臂聚合物的设计和制备.     

P(DEAM-co-NAS)的合成及其温敏性的环境效应

采用自由基溶液聚合法合成聚(N,N-二乙基丙烯酰胺-co-N-丙烯酸琥珀酰亚胺)(P(DEAM-co-NAS))共聚比为7.9∶1、3.5∶1、2.5∶1、2∶1、1.5∶1的五组共聚物.利用傅里叶变换红外(FTIR)光谱和核磁共振(1HNMR)谱对P(DEAM-co-NAS)结构进行表征.共聚物组成和介质性质对P(DEAM-co-NAS)水溶液温敏性有显著影响.结果表明:随着NAS含量增加,共聚物水溶液的低临界溶解温度(LCST)逐渐升高,温敏性降低;盐的引入使P(DEAM-co-NAS)水溶液的LCST降低,所引入盐的阴离子价数越高,影响程度越大;有机酸的引入使P(DEAM-co-NAS)水溶液的LCST降低;NaOH、乙二胺、丁二胺的引入使P(DEAM-co-NAS)水溶液的LCST升高,二胺对P(DEAM-co-NAS)水溶液温敏性影响程度要大于NaOH.     

棉纤维的N-异丙基丙烯酰胺接枝共聚及产物的温敏性研究

以硝酸铈铵(CAN)、过硫酸钾(KPS)及H2O2/H2A(双氧水/抗坏血酸)为引发体系,采用溶液自由基接枝法制备了具有温敏性的棉纤维N-异丙基丙烯酰胺接枝共聚物(cotton-g-PNIPAAm);在上述3种引发剂作用下的接枝反应可以达到的接枝率(G)排序为G(H2O2/H2A)>G(KPS)>G(CAN);研究了其他因素如引发剂浓度、反应时间、反应温度和单体浓度等对接枝率的影响,得出了优化的接枝反应条件;接枝样品的FTIR分析图谱和SEM观察均表明样品表面已接枝了聚N-异丙基丙烯酰胺;DSC分析显示,棉纤维N-异丙基丙烯酰胺接枝共聚物的低临界溶解温度(LCST)与纯的聚N-异丙基丙烯酰胺凝胶(LCST=32.48℃)相似,约为32~33℃;接枝率的变化对试样LCST的影响很小,但其可逆焓变(ΔH)会随接枝率的提高而增加;采用滴水试验法(AATCC 79)和毛效试验法(FZ/T 01071)检测棉纤维的N-异丙基丙烯酰胺接枝共聚物在不同温度时的吸水性变化,显示试样具有温敏特性,其中接枝率介于25%~45%的试样温敏性较高,过低或过高的接枝率均不利于获得高的温敏性;棉纤维的N-异丙基丙烯酰胺接枝共聚物试样的可逆焓变(ΔH)随试样膨胀/收缩时间变化的研究和分析结果表明,棉纤维的N-异丙基丙烯酰胺接枝共聚物对温度变化的响应比纯聚N-异丙基丙烯酰胺凝胶快.     

N-异丙基丙烯酰胺类共聚物温敏性研究

制备了N-异丙基丙烯酰胺(NIPAAm)与N,N-二甲基丙烯酰胺(DMAAm)和/或甲基丙烯酸羟乙酯(HEMA)的二元及三元共聚物,研究了组成和链转移剂用量对共聚物温敏性的影响,并在上述三元共聚物上接枝聚己内酯(PCL)得到温敏性两亲聚合物.结果表明,随着DMAAm增加、HEMA减少或共聚物分子量降低,共聚物的最低临界溶解温度升高,且PCL链段的接枝度和长度对聚合物的温敏性影响明显.     

含孪尾型丙烯酰胺的HAPAM在新胶束聚合体系中的制备及其疏水缔合性

以表面活性单体2-丙烯酰胺基十二烷磺酸钠(NaAMC12S)为表面活性剂构建了新的胶束共聚合体系,实施了丙烯酰胺(AM)与N,N-二正十二烷基丙烯酰胺(DiC12AM)的胶束共聚合,制备了含孪尾型丙烯酰胺的疏水缔合聚丙烯酰胺(HAPAM),该聚合物为三元共聚物DiC12AM/NaAMC12S/AM.通过控制共聚合条件,制得了微结构系列变化的共聚物;采用红外光谱法表征了三元共聚物的化学结构,用荧光探针法与表观粘度法重点研究了共聚物DiC12AM/NaAMC12S/AM的大分子链微结构与其疏水缔合性的关系.结果表明:新胶束共聚合体系大大简化了胶束的共聚合操作,而且由于表面活性单体进入共聚物主链,使三元共聚物DiC12AM/NaAMC12S/AM具有更强的疏水缔合性.与由单尾型丙烯酰胺N-正十二烷基丙烯酰胺(C12AM)为疏水单体制备的HAPAM相比,由DiC12AM制得的HAPAM疏水缔合性更为显著.     

CO2调控的温敏性聚合物的制备及其响应行为

通过原子转移自由基聚合制备了含甲氧基聚乙二醇(mPEG)、N-异丙基丙烯酰胺(PNIPAM)和2-(二乙基氨基)甲基丙烯酸乙酯(PDMAEMA)的三嵌段共聚物。该共聚物具有较为明显的温度响应特征,并且温敏性的范围可以通过CO₂进行调控。该三嵌段聚合物在水溶液中存在最低临界溶液温度(LCST),且该聚合物水溶液在CO₂调节的LCST下具有各种聚集状态。随着温度的升高,三嵌段聚合物表现出双重LCST行为,并最终导致PNIPAM嵌段和PDMAEMA嵌段分别在各自相转变温度下收缩,聚合物的疏水性增强,出现收缩-收缩-聚集的三相变过程。CO₂通过调控PDMAEMA嵌段中的叔胺基团电性,可以使聚合物的亲水性增强,使得三嵌段聚合物在较高温度下难以聚集,实现了CO₂对聚合物相转变温度的调控。      

表面活性单体NaAMC14S/丙烯酰胺共聚物的分子链微结构与疏水缔合性

在实施丙烯酰胺型阴离子表面活性单体2-丙烯酰胺基十四烷磺酸钠(NaAMC14S)与丙烯酰胺(AM)水溶液均相共聚合过程中,分别通过改变AM与NaAMC14S的投料比、改变外加电解质NaCl的加入量以及引发剂的用量,制备了分子链微结构系列变化的具有微嵌段结构的共聚物NaAMC14S/AM;采用荧光探针法与表观粘度法研究了共聚物分子链微结构与其疏水缔合性能之间关系,探索了共聚物分子链中疏水微嵌段含量、疏水微嵌段长度及共聚物分子量诸微结构因数对共聚物疏水缔合性的影响.结果表明,共聚物NaAMC14S/AM的疏水缔合性随着疏水微嵌段含量的增加而增强,随着疏水微嵌段长度的增长而增强,当疏水微嵌段含量和嵌段长度一定时,共聚物的疏水缔合性随分子量的增大而增强.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).     

Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: a non-product specific route to C-8 substituted analogues

Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO₄ oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.