PVA/PAA水凝胶纤维的电刺激响应性能

以过硫酸胺为引发剂,在PVA水溶液中原位聚合丙烯酸单体,得到的PVA／PAA混合水溶液在凝固浴硫酸胺饱和水溶液中纺丝制备了物理缠结和氢固定网络形式的PVA／PAA水凝胶纤维。该纤维于NaCl溶液中在直流电场作用下具有电流－刺激敏感性,表现为溶胀、收缩、弯曲行为。纤维的弯曲速度和最大弯曲度随电场强度和凝胶网络中PAA含量的增加而增大,随电解质溶液离子强度的变化出现临界最大值。纤维向负极弯曲的过程中,在电场下自由离子和反庆子迁移引起的渗透压主导作用,弯曲过程主要是溶胀弯曲;向正极弯曲过程中,由于电化学反应和电场作用下产生的PH梯度导致凝胶网络构像变化主导作用,弯曲主要是收缩弯曲;弯曲由负极向正极转化过程中,两种机理对弯曲的影响相对平衡。     

多壁碳纳米管/聚丙烯酸/MOF-5的制备及其N2吸附性能

用化学修饰法制备出复合物多壁碳纳米管/聚丙烯酸(MWCNTs/PAA),用溶剂热法合成Zn₄O(1,4-benzenedicarboxylate)₃(MOF-5)和MWCNTs/PAA/MOF-5。通过XRD、FTIR、TG、HRTEM和比表面积和孔隙度分析仪对MWCNTs,MOF-5,MWCNTs/PAA和MWCNTs/PAA/MOF-5的结构和性质进行表征。结果表明:复合材料MWCNTs/PAA中PAA包覆在碳纳米管外壁上,含量为4.3%,在FTIR中有PAA特征官能团的吸收峰;MWCNTs/PAA/MOF-5和MOF-5的形貌一样,MWCNTs/PAA/MOF-5的热分解温度比MOF-5的提高了49℃;MOF-5和MWCNTs/PAA/MOF-5的N₂吸附曲线为Ⅰ型,77K和100kPa条件下,N₂的吸附量达到最大值,分别为265、299.03 cm³·g^-1。     

多壁碳纳米管/聚丙烯酸/MOF-5的制备及其N_2吸附性能

用化学修饰法制备出复合物多壁碳纳米管/聚丙烯酸(MWCNTs/PAA),用溶剂热法合成Zn4O(1,4-benzenedicarboxylate)3(MOF-5)和MWCNTs/PAA/MOF-5。通过XRD、FTIR、TG、HRTEM和比表面积和孔隙度分析仪对MWCNTs,MOF-5,MWCNTs/PAA和MWCNTs/PAA/MOF-5的结构和性质进行表征。结果表明:复合材料MWCNTs/PAA中PAA包覆在碳纳米管外壁上,含量为4.3%,在FTIR中有PAA特征官能团的吸收峰;MWCNTs/PAA/MOF-5和MOF-5的形貌一样,MWCNTs/PAA/MOF-5的热分解温度比MOF-5的提高了49℃;MOF-5和MWCNTs/PAA/MOF-5的N2吸附曲线为Ⅰ型,77 K和100 k Pa条件下,N2的吸附量达到最大值,分别为265、299.03 cm3·g-1。     

聚酰胺酸湿法纺丝凝固过程三元相图的初步构建

利用浊点滴定法构建了聚酰胺酸(PAA)/N,N-二甲基乙酰胺(DMAc)/水(H2O)体系的三元相图.研究了PAA的特性黏数和分子结构变化对三元相图的影响.结果表明,PAA/DMAc/H2O三元体系只发生液-液相分离;相转变时体系的组成配比存在线性关系.在一定范围内,PAA特性黏数的变化基本不影响体系三元相图的构成.不同分子结构PAA的三元体系,其相分离过程对温度的敏感程度不同.     

聚丙烯酸水溶液及α-A12O3悬浮液的流变性研究

研究了pH、聚丙烯酸(PAA)浓度和分子量对PAA水溶液的粘度的影响,发现溶液的流变行为与溶液中PAA高分子链的离子化程度和构型密切相关,高分子链刚性程度的增加和链的伸展使溶液在pH为7～9时的粘度最大;研究了在PAA溶液中引入陶瓷粉体后悬浮液的粘度变化,发现当陶瓷粉体和PAA的量达到一定比值时悬浮液体系的粘度达到最小值,同时发现陶瓷粉体的粒径大小与这一粘度最小值和悬浮液流变特性也有关.     

聚丙烯酸对自然水体生物膜吸附镉的影响

选择聚丙烯酸(PAA)为水中溶解态高分子天然有机质的代表, 研究了PAA对自然水体生物膜吸附重金属Cd的影响, 包括不同浓度的PAA对吸附的影响, PAA对特定pH下吸附等温线的影响以及不同pH下按不同顺序添加PAA时对吸附的影响. 研究结果表明, PAA的存在一般会降低生物膜对Cd的吸附, 其影响程度与PAA的浓度、 溶液pH、 吸附顺序及生物膜厚度等有关. PAA与Cd的浓度比越高, 其对吸附的影响越显著. 吸附溶液pH越高, PAA的影响越显著. 吸附顺序对吸附的影响在pH较低时不明显, 当pH较高时, 先加PAA后加Cd及两者同时吸附时对吸附的降低作用接近且较大, 先加Cd后加PAA时对吸附的降低作用相对较小. 生物膜较薄时PAA的影响更显著. PAA对生物膜吸附Cd的影响主要由PAA与生物膜之间对Cd的竞争以及三元表面配合物的生成与吸附2种因素共同决定. 高pH会促进PAA与Cd的配合而不利于带负电的配合物在生物膜上的吸附.     

分散剂PAA在核电厂凝结水精处理树脂上的吸附特性研究

乙醇胺(Ethanolamine,ETA)与分散剂在核电站二回路中联合使用具有广阔的应用前景,但典型分散剂聚丙烯酸(Polyacrylic acid,PAA)对凝结水精处理树脂的影响有待研究。本文研究了PAA与罗门哈斯树脂的相容性问题,探讨了PAA对树脂的吸附特性及对工作交换容量的影响,并给出了树脂的解吸(再生)方法。实验结果表明,PAA会导致树脂工作交换容量下降,随着PAA浓度的增加,树脂污染加剧,且阴树脂污染比阳树脂严重;吸附过程为吸热过程,Langmuir方程能更准确描述罗门哈斯阴树脂对PAA的吸附过程,25℃时按Langmuir方程得到的最大吸附量为8.8339mg/g,与实验结果相近;PAA在阴树脂上的吸附行为符合拟二级动力学方程,颗粒扩散过程为吸附的控速步骤,平衡吸附量Qe的理论值(9.142mg/g)与实验值(8.548mg/g)基本一致;解吸配方与步骤可以满足阴树脂的再生要求,本文研究结果对核电站二回路PAA的使用有一定的参考与借鉴意义。     

聚丙烯酸在纳米TiO2表面吸附行为的研究

讨论了聚丙烯酸在纳米TiO₂水悬浮体系中的吸附行为.红外光谱分析和吸附实验结果表明,纳米TiO₂通过氢键吸附PAA.PAA吸附量随着浓度的升高而增大直至饱和吸附量,且分子量越大,饱和吸附量越大.pH值增大,则饱和吸附量减小.在相同条件下,表面吸附层的厚度随PAA分子量、浓度和pH值增大而增大.这是由PAA在颗粒表面构型的变化所致.吸附PAA后的纳米TiO₂的表面电荷密度和ζ电位发生变化,pHiep值向低值方向移动.表面吸附自由能的计算结果说明,PAA在纳米TiO₂表面的吸附是自发过程.     

PAA对PLA流变性能和热性能的影响

通过熔融共混法制备了一系列的PLA/PAA共混物,考察了PLA/PAA共混体系的流变行为和热性能(结晶行为和热降解行为).FTIR测试结果证实PLA与PAA分子链之间形成了氢键网络.动态剪切流变测试和DSC测试均表明共混体系的流变行为和冷结晶行为会随着PAA含量的改变而改变,这可能是由于PLA与PAA的氢键作用受到PAA含量的影响.另外,DSC测试证实共混体系中的氢键网络还会受到试样热历史的影响.当PAA含量较低(低于5 wt%)时,PLA/PAA共混体系中PAA与PLA熔体两相的相分离不严重,使得PAA与PLA分子链能够较大限度地接触而形成较强的氢键作用,因而可以明显减缓增塑作用对黏度降低的影响.     

The role of hydrogen-bonding interaction in poly(vinyl alcohol)/poly(acrylic acid) blending solutions and their films

<正>The aim of this work is to investigate the hydrogen-bonding interaction in poly(vinyl alcohol)(PVA)/poly(acrylic acid)(PAA) blending system and its influence on rheological properties in solution and the physical properties in solid state. Introducing PAA into PVA solutions resulted in a thickening behavior of blend solutions.The viscosity of the solutions increased with PAA content increasing,and a maximum viscosity could be obtained when the ratio of PVA/PAA was 70/30. The intermolecular hydrogen-bonding and miscibility between PVA and PAA in solid state were investigated by differential scanning calorimetry(DSC),Fourier transform infrared spectroscopy(FTIR) and mechanical measurements.The results displayed the great influence of introducing PAA on the properties of blending films.The tensile strength increased from 89.31 MPa to 119.8 MPa and Young's modulus improved by over 300%with increasing PAA concentration compared with those of pure PVA films.By systematically studying the rheological behaviors of solutions and the physical properties of films,the influence of hydrogen-bonding in solutions and solid states were discussed.     

Evidence of aggregation in dilute solution of amphoteric poly(amido-amine)s by size exclusion chromatography

Evidence of aggregation of amphoteric linear poly(amido-amine)s (PAAs) was proved using a multi-angle laser light scattering detector on-line to a size exclusion chromatography (SEC) system. As a rule the PAAs chemical structure, with the presence of charged groups that are both anionic and cationic, easily generates aggregation and non-steric fractionation. A non-amphoteric, non-aggregate PAAs polymer with an elution pattern close to ideal SEC was also obtained and characterized for comparison. The influence of PAAs synthesis conditions on the extent of aggregation was also studied.     

Complexation of Cu(II) Ions with the lowest generation poly(amido-amine)-OH dendrimers: a molecular simulation study

Classical molecular dynamics simulations and density functional theory calculations are performed to obtain insights about the attachment of the copper(II) ion to the lowest generation poly(amido-amine) dendrimer, G0-OH, in aqueous solutions. Various initial configurations of the ion relative to the dendrimer sites are tested and it is concluded that both the solvent as well as-in a lesser degree for low generation dendrimers-the folding of the dendrimer branch play an important role in copper(II) ion complexation. The presence of solvent and branch folding retain the ion close to the atomic binding sites consisting mainly of amide oxygen as well as hydroxyl oxygen but also tertiary amine nitrogen. A discussion of currently available experimental results in Cu(II) complexation in larger generation dendrimers is provided.     

细胞膜仿生修饰树枝状聚酰胺-胺的研究

利用2-丙烯酰氧基乙基磷酸胆碱的双键与树枝状聚酰胺-胺表面的氨基进行Michael加成反应,实现树枝状聚酰胺-胺表面的磷酸胆碱仿生修饰,修饰过程用FTIR、1H-NMR进行了表征.体外细胞活性测定和细胞形貌观察证实磷酸胆碱仿生修饰有效地改善了聚酰胺-胺树枝状聚合物的生物相容性;修饰后的聚酰胺-胺树枝状聚合物表面剩余的氨基仍然可以有效的与DNA复合,有可能作为一种潜在的基因载体得到广泛应用.     

Novel poly(amido-amine)-based hydrogels as scaffolds for tissue engineering

Biodegradable and biocompatible amphoteric poly(amido-amine) (PAA)-based hydrogels, containing carboxyl groups along with amino groups in their repeating unit, were considered as scaffolds for tissue engineering applications. These hydrogels were obtained by co-polymerising 2,2-bisacrylamidoacetic acid with 2-methylpiperazine with or without the addition of different mono-acrylamides as modifiers, and in the presence of primary bis-amines as crosslinking agents. Hybrid PAA/albumin hydrogels were also prepared. The polymerisation reaction was a Michael-type polyaddition carried out in aqueous media. The PAA hydrogels were soft and swellable materials. Cytotoxicity tests were carried out by the direct contact method with fibroblast cell lines on the hydrogels both in their native state (that is, as free bases) and as salts with acids of different strength, namely hydrochloric, sulfuric, acetic and lactic acid. This was done in order to ascertain whether counterion-specific differences in cytotoxicity existed. It was found that all the amphoteric PAA hydrogels considered were cytobiocompatible both as free bases and salts. Selected hydrogels samples underwent degradation tests under controlled conditions simulating biological environments, i.e. Dulbecco medium at pH 7.4 and 37 degrees C. All samples degraded completely and dissolved within 10 d, with the exception of hybrid PAA/albumin hydrogels that did not dissolve even after eight months. The degradation products of all samples turned to be non-cytotoxic. All these results led us to conclude that PAA-based hydrogels have a definite potential as degradable matrices for biomedical applications.     

Ab initio Study of Complexation Process between Poly(amido-amine) and Nano-Silicon Dioxide

To understand better the molecular-level details of ≡Si⁺(SC) or ≡SiO^-(SOA) ion group to -NH₂ teminated poly(amido-amine) dendrimers in the gas phase, density functional theory is used to optimize the minimum energy and transition state structures with UB3LYP/6-311G(d) and HF/6-31G levels. The tertiary amine nitrogen and the amide oxygen are found to be the most favorable binding sites. The activation energies of the different active sites and the reaction steps of SC and/or SOA ion group and the amide sites are also analyzed. The stable compounds are formed via the electrostatic interaction and the coordination effect. The orientation of the amide O and the rotation of the branches minimizes the energy of the whole system.     

The protonation thermodynamics of cyclodextrin-containing polymers for drug inclusion

A poly(amido-amine), PAA, bearing β-CD units in the side chain was synthesized by a polyaddition reaction of 1,4-bis-acryloyl-piperazine with 6-monodeoxy-6-monoamino-β-cyclodextrin (β-CD-NH₂). Unlike the simple β-CD-NH₂ with a greater basicity constant (log K = 8.60), the polymer revealed an unusual polyelectrolyte behaviour with a lower basicity constant (log K° = 6.29) of the tertiary nitrogen atom, that is strongly dependent on the degree of protonation α of the whole macromolecule. It follows the modified Henderson–Hasselbalch equation with n = 1.75, in a wide α-range. The greater (?46.1 kJ/mol) and the lower (?27.6 kJ/mol) enthalpy (ΔH°) changes of the compounds were in line with the protonation of a primary or a tertiary nitrogen atom. The calorimetric data suggested that the PAA protonation destroyed a packing structure formed by two rigid β-CD side chains interacting head-to-head. The UV spectrophotometric data showed that the PAA exhibits affinity towards the l-ascorbic acid at low pH (pH 2.46) with an isosbestic point at 241 nm and a slight blue shift of the maximum absorption of the ascorbic acid (244 nm) on PAA additions.     

Kinetics and structure-activity relationship of dendritic bridged hindered phenol antioxidants to protect styrene against free radical induced peroxidation

A series of dendritic poly(amido-amine) (PAMAM) bridged hindered phenols antioxidants were synthesized. The active antioxidant group (3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid) was attached to two generations of PAMAM dendrimers, and their structure was verified by nuclear magnetic resonance (NMR) and fourier transform infrared spectra (FT-IR). The antioxidant abilities of the dendritic phenols to inhibit the oxidation of styrene were evaluated and the relationships between the length of core, the generation of dendrimers and the antioxidant activities were established. The reaction kinetics of scavenging peroxyl radicals was followed by oxygen consumption. The inhibition time (t_inh) values showed the dendritic phenols had the ability of scavenging peroxyl radicals, and that the antioxidant ability increased with the increasing length of the core and the generation. The kinetic analysis demonstrated that dendritic phenols could slow the rate of styrene peroxidation induced by AIBN, as shown by the number of trapping ROO· (n), and this role was in accordance with that of the t_inh values.     

A NOVEL NANOFILTRATION MEMBRANE PREPARED WITH PAMAM AND TMC (I)

A series of nanofiltration (NF) membranes were prepared with poly(amido-amine) (PAMAM) and trimesoyl chloride (TMC) viu in situ interfacial polymerization.The effects of the generation number and concentration of PAMAM on the properties of NF membranes were discussed.Fourier transform infrared spectroscopy (FTIR-ATR),atomic force microscopy (AFM),scanning electron microscopy (SEM) and contact angle measurements were employed to characterize the resulting membranes.The nanofiltration performances were evaluated with solutions of NaCl,Na2SO4,MgCl2 and MgSO4,respectively.FTIR-ATR spectra indicated that TMC reacted more sufficiently with the higher generation PAMAM.The salts rejection of the resulting membranes increased with increasing the generation number of PAMAM,which was mainly attributed to the concentration difference of terminal amino-groups among the different generation PAMAM.The MgCl2 (2000 mg/L) rejection of NF-G5 reached 90.3% under the pressure of 0.6 Mpa in a cross-flow method measurement.The rejection of MgCl2 increased with increasing concentration of PAMAM.The salts rejection order of NF membranes with high rejection is MgCl2>MgSO4>Na2SO4>NaCI.It was also found that the NF-Gx (x=4,5,6,7) membranes became more hydrophilic with increasing the generation number of PAMAM.     

A NOVEL NANOFILTRATION MEMBRANE PREPARED WITH PAMAM AND TMC (Ⅰ)

A series of nanofiltration (NF) membranes were prepared with poly(amido-amine) (PAMAM) and trimesoyl chloride (TMC) via in situ interfacial polymerization.The effects of the generation number and concentration of PAMAM on the properties of NF membranes were discussed.Fourier transform infrared spectroscopy (FTIR-ATR),atomic force micrgscopy (AFM),scanning electron microscopy (SEM) and contact angle measurements were employed to characterize the resulting membranes.The nanofiltration performances were eva...     

Stereoblock poly(lactic acid): synthesis via solid-state polycondensation of a stereocomplexed mixture of poly(L-lactic acid) and poly(D-lactic acid)

Stereoblock poly(lactic acid) consisting of D- and L-lactate stereosequences can be successfully synthesized by solid-state polycondensation of a 1:1 mixture of poly(L-lactic acid) and poly(D-lactic acid). In the first step, melt-polycondensation of L- and D-lactic acids is conducted to synthesize poly(L-lactic acid) and poly(D-lactic acid) with a medium-molecular-weight, respectively. In the next step, these poly(L-lactic acid) and poly(D-lactic acid) are melt-blended in 1:1 ratio to allow formation of their stereocomplex. In the last step, this melt-blend is subjected to solid-state polycondensation at temperature where the dehydrative condensation is allowed to promote chain extension in the amorphous phase with the stereocomplex crystals preserved. Finally, stereoblock poly(lactic acid) having high-molecular-weight is obtained. The stereoblock poly(lactic acid) synthesized by this way shows a higher melting temperature in consequence of the controlled block lengths and the resulting higher-molecular-weight. The product characterization as well as the optimization of the polymerization conditions is described. Changes in M(w) of stereoblock poly(lactic acid) (sb-PLA) as a function of the reaction time.