温敏性嵌段共聚物纳米胶束的制备及其稳定性

通过N-异丙基丙烯酰胺(NIPAAm)和N,N-二甲基丙烯酰胺(DMAAm)在链转移剂巯基乙醇存在下的自由基共聚,制备了具有端羟基的共聚物P(NIPAAm-co-DMAAm).利用其端羟基在异辛酸亚锡催化下引发己内酯开环聚合,得到了两亲性嵌段共聚物P(NIPAAm-co-DMAAm)-b-PCL,并在聚己内酯(PCL)链末端引入可光催化反应的不饱和双键.通过1H-NMR、GPC和相转变温度(LCST)等方法对聚合物进行了结构表征,测定了嵌段共聚物形成胶束的临界胶束浓度和胶束粒径,比较了核交联前后胶束的粒径和稳定性.结果表明:通过调节共聚物的组成,可获得LCST在40℃附近的胶束,胶束经核交联后,粒径有所减小,但稳定性明显提高,可用于对药物的温敏控制释放.     

丙烯腈-N-异丙基丙烯酰胺接枝共聚物的合成及其对聚丙烯腈分离膜的改性

以巯基乙胺盐酸盐(AESH)为链转移剂、2,2'-偶氮二异丁腈为引发剂,合成了具有端氨基的聚(N-异丙基丙烯酰胺)(PNIPAAm);与甲基丙烯酰氯反应,得到可聚合的PNIPAAm大分子单体;进而与丙烯腈共聚,合成了丙烯腈-N-异丙基丙烯酰胺接枝共聚物(P(AN-g-NIPAAm)).基于浸没沉淀相转化法制备了聚丙烯腈/P(AN-g-NIPAAm)共混膜.红外及核磁分析表明,通过调控AESH的浓度可制备得到不同链长的PNIPAAm大分子单体;用激光光散射进一步测定了共聚物的重均分子量;采用鼓泡接触角及浊度测定考察了共聚物的温敏特性;XPS结果证实PNIPAAm链在膜表面发生富集;纯水压滤实验发现所制备的分离膜40℃(高于PNIPAAm的LCST)时的水通量是25℃(低于PNIPAAm的LCST)时的近2倍,具有较明显的温敏性.     

含疏水链节的聚N-异丙基丙烯酰胺共聚物的温敏性

采用溶液聚合法合成了一系列N-异丙基丙烯酰胺(NIPAM)与甲基丙烯酸甲酯、丙烯酸乙酯、丙烯酸丁酯或甲基丙烯酸丁酯的无规共聚物,用浊度观测法和光散射法测定了不同共聚物水溶液的温敏相转变行为.结果表明:所得共聚物的低临界溶解温度(LCST)均低于均聚物PNIPAM的,酯类单体的结构和含量对共聚物的LCST有显著影响,其中酯基上的烷基对共聚物LCST的影响能力大于丙烯酸酯α位上的烷基,前者对增大共聚物的疏水性有更大贡献.通过NIPAM与特定丙烯酸酯单体进行无规共聚可以合成转变温度低于PNIPAM均聚物且具有预设LCST数值的水溶性温敏聚合物.     

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.     

温敏性含氟两亲接枝共聚物的制备及胶束化行为

以聚乙二醇单甲醚甲基丙烯酸酯(MPEGMA)为大分子单体, 甲基丙烯酸六氟丁酯(HFMA)为含氟单体, N-异丙基丙烯酰胺(NIPAAm)为功能性单体, 采用大分子单体接枝共聚法, 制备了一种温敏性含氟两亲接枝共聚物P(NIPAAm-co-HFMA)-g-PEG. 利用FTIR, ¹H NMR, ¹⁹F NMR和GPC对共聚物的结构进行表征; 采用紫外-可见分光光度计测定了共聚物的低临界溶解温度(LCST)约为38.9 ℃, 高于人体正常的生理温度; 利用荧光探针技术测定了共聚物的临界胶束浓度(cmc), 结果表明, 当共聚物溶液温度高于LCST时, 其cmc明显变小; 利用激光光散射粒度仪(LLS)测定了共聚物胶束的水合粒径及其分布, 当温度达到LCST时, 胶束粒径明显变小, 温度过高时, 粒径又有所增大; 利用透射电子显微镜(TEM)研究了共聚物胶束的形貌, 结果表明, P(NIPAAm-co-HFMA)-g-PEG在水溶液中可自组装成球状胶束粒子, 随着温度的升高, 共聚物胶束由松散的核壳结构转变成更加紧凑的球状结构, 且粒径明显变小.     

聚丙烯酸-b-聚(N-异丙基丙烯酰胺)嵌段共聚物的合成及其温度和pH值敏感性自组装研究

通过原子转移自由基聚合方法, 在丁酮/异丙醇混合溶剂中合成了分子量可控和分布较窄的聚丙烯酸叔丁酯-b-聚N-异丙基丙烯酰胺(PtBA-b-PNIPAM)嵌段共聚物, 用GPC和 1 H NMR对其结构进行了表征. PtBA-b-PNIPAM在甲苯中水解得到聚丙烯酸-b-聚N-异丙基丙烯酰胺(PAA-b-PNIPAM). 用动态光散射技术对PAA-b-PNIPAM在水溶液中的自组装行为随pH值和温度变化的响应进行了初步研究.     

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。     

双重响应性核交联星型聚合物的合成及其性能研究

通过"臂优先"的途径和可逆加成-断裂转移(RAFT)自由基聚合制备了以p H响应性聚(3-丙烯酰胺基苯硼酸-co-丙烯酰胺)(PAA-DMP)为线性外臂,温敏性聚(N-异丙基丙烯酰胺-co-苯乙烯-co-N,N-亚甲基双丙烯酰胺)(PNSB)为核的核交联星型聚合物(PNSB@PAA-DMP).采用傅里叶红外光谱(FTIR)、核磁氢谱(1H-NMR)和凝胶渗透色谱(GPC)对产物进行了表征.粒径和形貌也分别通过动态光散射(DLS)和透射电子显微镜(TEM)做了表征.采用紫外可见光谱(UV-Vis)和动态光散射(DLS)考察了聚合物在水中的相变行为.结果表明,所制备的核交联星型聚合物具有p H和温度双重响应,其低临界溶解温度(LCST)可以通过改变核内聚苯乙烯的量来进行调节.除此之外,在高浓度(20 mg/m L)下,还可以通过控制温度和p H实现聚合物溶液溶胶-凝胶(sol-gel)的转化.     

聚-N-异丙基丙烯酰胺的制备及应用进展

聚(N-异丙基丙烯酰胺)(PNIPAM)是一种温敏性高分子聚合物,在最低临界溶解温度(LCST)处会发生构象转变。对PNIPAM加以改性,可拓宽温敏性聚合物材料的研究领域,使其在药物负载运输、基因传递、化学分析和表面浸润性等领域发挥更大的应用价值。本文对PNIPAM的活性自由基聚合方法及其应用进展进行了综述,并展望了其发展前景。     

温度响应型手性Salen Ti~(IV)嵌段共聚物的可控制备及在硫醚不对称氧化反应中的应用

采用可逆加成-断裂链转移自由基聚合法(RAFT),以N-异丙基丙烯酰胺和5-乙烯基手性salen Ti~(IV)为反应单体,偶氮二异丁腈为链引发剂,硫代丙酸苄硫酯为链转移剂,可控制备出一系列温度响应型手性嵌段共聚物(聚N-异丙基丙烯酰胺-co-手性salen Ti~(IV),PNxSy).通过红外表征证明该嵌段共聚物结构中含有温敏材料和salen Ti~(IV)的特征峰,紫外表征揭示了亲疏水单元比例对嵌段共聚物临界温度LCST的影响,动态光散射证明亲疏水比例对嵌段共聚物水合动力学粒径影响规律.透射电子显微镜和圆二色光谱表征温度对嵌段共聚物自组装的影响,结果表明,接近临界温度30℃时,嵌段共聚物的CD信号最强.该类温度响应型手性嵌段共聚物可实现纯水相中高效不对称反应的进行,仅需0.5 mol%嵌段共聚物催化反应1.0 h,即可实现底物苯甲硫醚转化率达95%,选择性为97%,对映选择性高达98%.实验证明嵌段共聚物在水中可自组装形成纳米反应器,加速反应进行,升温后,嵌段共聚物表现出疏水特性,从水相析出后直接回收,实现了材料可重复利用.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.