纳米羟基磷灰石表面接枝聚合左旋丙交酯

为了改善HA纳米粒子与有机PLGA的相容性,分别采用六亚甲基二异氰酸酯加乙二醇、左旋乳酸改性纳米粒子表面后或直接原位接枝聚合左旋丙交酯等3种不同方法,制备了表面修饰聚乳酸的纳米羟基磷灰石(PLLA-g-HA).FTIR、XPS、TEM、TGA测试表明PLLA成功接枝到HA的表面.其中六亚甲基二异氰酸酯加乙二醇改性HA纳米粒子所获得的PLLA接枝率远高于其它两种方法达25%,调整有机相和无机相的比例对PLLA接枝率的影响较小,其在氯仿中可以稳定分散2天以上.共混电纺丝后的拉伸测试表明PLLA-g-HA/PLAG复合纤维膜的力学性能高于HA/PLGA膜,当两者之间的比例为5%拉伸性能达到最大值.     

聚乙烯醇/层状双金属氢氧化物复合膜的原位制备及其性能研究

采用一步水热法,原位制备了聚乙烯醇(PVA)/层状双金属氢氧化物(LDH)复合材料(PVA/LDH).与溶液共混法相比,原位生成法具有实验操作简单、制备周期短等优势.广角X射线衍射(WXRD)结果显示,利用该方法可在PVA溶液中原位生成晶型完整的LDH片状粒子.与溶液共混法制备所得复合体系的流变行为不同,原位合成体系在低剪切速率下的表观黏度随LDH含量的增加而下降.得益于LDH在PVA中的良好分散,填料含量为1.0 wt％时,复合膜的力学拉伸强度及弹性模量较纯PVA膜分别提高105.40％和133.20％.在保持复合材料高透光性基础上,薄膜的耐水性也有一定的提升,但其耐水蒸汽的提高仅当LDH含量达3.0 wt％才有所体现.     

型胶原在聚-L-乳酸(PLLA)表面的化学接枝和涂层及其对软骨细胞生长的促进作用

采用接枝-涂层技术在聚-L-乳酸(PLLA)膜表面接枝聚甲基丙烯酸(PMAA)得到稳定的PLLA-g-PMAA胶原涂层.利用水溶性碳化二亚胺作为缩合剂,使PLLA-g-PMAA表面的羧基和胶原分子中的氨基发生缩合反应,从而将型胶原接枝在PLLA表面;同时保留材料表面物理涂层的胶原溶液,获得了稳定的胶原涂层.XPS谱图证实了接枝反应的发生.分别用比色法和茚三酮法测定了PLLA-g-PMAA表面的羧基密度和PLLA膜表面胶原的接枝量和涂层量.细胞培养结果表明,改性后的PLLA膜表面软骨细胞的铺展性能和增长速度明显改善.     

型胶原在聚-L-乳酸(PLLA)表面的化学接枝和涂层及其对软骨细胞生长的促进作用

采用接枝 -涂层技术在聚 -L-乳酸 ( PLLA)膜表面接枝聚甲基丙烯酸 ( PMAA)得到稳定的 PLLA-g-PMAA胶原涂层 .利用水溶性碳化二亚胺作为缩合剂 ,使 PLLA-g-PMAA表面的羧基和胶原分子中的氨基发生缩合反应 ,从而将 型胶原接枝在 PLLA表面 ;同时保留材料表面物理涂层的胶原溶液 ,获得了稳定的胶原涂层 . XPS谱图证实了接枝反应的发生 .分别用比色法和茚三酮法测定了 PLLA-g-PMAA表面的羧基密度和 PLLA膜表面胶原的接枝量和涂层量 .细胞培养结果表明 ,改性后的 PLLA膜表面软骨细胞的铺展性能和增长速度明显改善 .     

二氧化钛纳米棒/二氧化硅核壳粒子的制备及在聚乳酸中的应用

以三氯化钛为钛源合成了纯金红石型Ti O2纳米棒,用正硅酸乙酯对纳米Ti O2表面进行修饰,得到Si O2为壳,Ti O2为核的纳米粒子(Si O2@Ti O2),Ti O2纳米棒的平均长度约为50 nm,平均直径约为8 nm,Si O2包覆层的厚度约为4 nm,Si O2@Ti O2的最大吸收波长较Ti O2的最大吸收波长存在微弱蓝移.采用熔融共混法制备聚左旋乳酸(PLLA)/(Si O2@Ti O2)纳米复合材料.采用透射电子显微镜(TEM)、热失重分析(TGA)、差示扫描量热分析(DSC)、紫外-可见吸收光谱(UV-Vis)和二维广角X射线散射(2D-WAXS)等研究了Si O2@Ti O2的加入对PLLA耐热性能、结晶性能、紫外线屏蔽性能及拉伸性能的影响.结果表明,Si O2@Ti O2在PLLA基体中分散较好,Si O2@Ti O2提高了PLLA的热分解温度,具有异相成核的作用.PLLA/(Si O2@Ti O2)纳米复合材料薄膜在保持较高可见光透过率的同时具有优异的紫外线屏蔽性能.Si O2@Ti O2的加入使PLLA在较高温度下拉伸时能够获得更高的结晶度和取向度.     

左旋聚乳酸/聚己内酯/氧化锌复合材料的制备及性能

基于左旋聚乳酸（PLLA）固有低韧性的缺点,分别引入可降解且柔韧性好的聚己内酯（PCL）和刚性纳米粒子氧化锌（nano-ZnO）对其改性,通过溶液共混的方法制备了PLLA/PCL/ZnO复合材料。借助DSC、DMA考察了复合材料的热行为和粘弹性,研究发现,PCL和ZnO的引入对PLLA复合材料的玻璃化转变温度没有影响,说明复合材料是不相容体系;随着PCL、ZnO含量的增多,PLLA的熔融峰向低温偏移。拉伸实验结果表明,PLLA/2%PCL/1%ZnO组分的复合材料拉伸韧性最佳,断裂伸长率达到了35%,比纯PLLA的断裂伸长率提升了20倍。然而,相同比例的PCL和ZnO单独对PLLA改性时,断裂伸长率分别为17%和4%,说明两者协同作用的增韧效果更好。拉伸断面的观察结果表明,PCL/ZnO含量增多时PCL分散相尺寸增大、相分离显著,且ZnO粒子趋于聚集,因而导致增韧效率下降。     

聚左旋乳酸/聚氧化乙烯共混物的拉伸行为及结构转变

采用熔融共混方法制备了聚左旋乳酸(PLLA)和超高分子量聚氧化乙烯(PEO)共混物, 通过差示扫描量热(DSC)、 扫描电子显微镜(SEM)和二维广角X射线散射(2D-WAXS)等方法系统研究了PEO的加入对不同温度下PLLA拉伸行为及拉伸过程中微观结构变化的影响. 结果表明, PLLA/PEO共混物为非均相体系, PEO粒子均匀分布在PLLA中形成两相结构. PEO的加入能够显著降低PLLA的玻璃化转变温度(T_g), 在25～60 ℃范围内显著提高PLLA的拉伸性能. 在60 ℃拉伸时, PEO的加入提高了PLLA在拉伸过程中的结晶和形变能力. 在80 ℃拉伸时, 共混物的拉伸断裂伸长率下降, 但共混物的结晶速度仍高于纯PLLA样品.     

聚L-乳酸/二氧化硅纳米复合材料及其表面诱导生成类骨磷灰石的制备

为改善纳米SiO2粒子在聚L-乳酸基体中的分散性, 将乳酸齐聚物接枝到纳米SiO2粒子表面, 通过IR, 29Si MAS NMR和TGA对改性SiO2进行表征. 以聚L-乳酸(PLLA)为基体, 加入乳酸齐聚物接枝改性的二氧化硅(g-SiO2)粒子, 采用溶液浇铸法制备PLLA/g-SiO2纳米复合材料, 测试其在模拟体液(SBF)中的生物活性. 通过XRD, IR, SEM和EDS表征手段, 考察材料表面类骨磷灰石形成能力. 结果表明, 乳酸齐聚物成功地接枝到SiO2表面, 当反应36 h时, g-SiO2接枝率最大(9.22%). 随着g-SiO2含量增加和浸泡时间的延长, 材料表面最初形成的无定形沉积物矿化成碳酸羟基磷灰石(Carbonated hydroxyapatite, CHA), 钙磷比为1.72, 类似于人骨无机质, 表明g-SiO2的引入能明显加速复合材料表面CHA沉积, 该复合材料有望成为骨修复填充材料和组织工程支架材料.     

含柔性链段聚右旋乳酸嵌段共聚物对聚左旋乳酸拉伸行为的影响

采用聚右旋乳酸(PDLA)与聚乙二醇(PEG)的三嵌段共聚物(PDLA-b-PEG-b-PDLA)对聚左旋乳酸(PLLA)进行改性,系统研究熔融共混法制备的PLLA/PDLA-b-PEG-b-PDLA共混物的热性能和不同温度下的拉伸行为,并通过原位X射线散射(WAXS)技术探索不同含量的PDLA-b-PEG-b-PDLA对PLLA在拉伸过程中结晶行为的影响.结果表明,加入PDLA-b-PEG-b-PDLA对PLLA的热稳定性影响较小;PLLA/PDLA-b-PEG-b-PDLA共混物中由于立构晶的存在,能有效提高PLLA的α晶的结晶速率;室温(30°C)拉伸时,样品均呈现脆性断裂;拉伸温度提高至50°C,纯PLLA和PLLA/PDLA-b-PEG-b-PDLA(95/5)的共混物仍然呈现脆性断裂,但是随着PDLA-b-PEG-b-PDLA含量的增加,PLLA发生屈服,断裂伸长率由纯PLLA的10%左右提高至200%以上;80°C拉伸时,PDLA-b-PEG-b-PDLA的加入显著提高了PLLA在拉伸过程中的结晶速率,出现α晶的应变从纯PLLA的400%降低至50%以下,立构晶含量在拉伸过程中基本保持不变.上述结果显示含柔性链段的PDLA的嵌段共聚物可有效提高PLLA的结晶速率和延展性,拓宽PLLA的应用范围.     

聚癸二酸丙三醇酯对聚乳酸的改性

以丙三醇和癸二酸为单体通过熔融缩聚制得了聚癸二酸丙三醇酯(PGS),并用其预聚物(p-PGS)对聚L-丙交酯(PLLA)进行共混改性.利用傅立叶变换红外光谱(FT-IR)、核磁共振氢谱(1H-NMR)及凝胶渗透色谱(GPC)法对P-PGS的结构进行表征,并研究了改性后材料的力学性能、两相相容性、亲水性能和细胞相容性.结果表明:P-PGS具有支化分子结构,分散系数约为2.7;共混改性后的材料弹性模量和拉伸强度均有所下降,而断裂伸长率从7 %显著提高到150%左右;PLLA/PGS属于海岛式共混结构,PGS以小于10μm的尺寸均匀分布在PLLA基体中;共混后材料的亲水性也有一定的提高,且几乎保持了PLLA原有的细胞相容性.     

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%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

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.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

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.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.