等离子体引发丙烯酰胺水溶液聚合

用两种等离子体引发丙烯酰胺水溶液聚合的方法 ,制备了线性超高分子量聚丙烯酰胺 .研究了放电时间、放电功率、单体的初始浓度及溶液的pH值等对聚合产物的影响     

丙烯酰胺聚合物与氧化铝晶体相互作用的分子动力学模拟

将丙烯酰胺单体分别与丙烯酸(AA)、阳离子单体丙烯酰氧乙基二甲基乙基溴化铵(DMB)、疏水性单体丙烯酸十八酯(OA)共聚,分别得到阴离子聚丙烯酰胺P(AA-co-AM)、阳离子聚丙烯酰胺P(DMB-co-AM)、非离子聚丙烯酰胺P(AM)和疏水性聚丙烯酰 胺P(OA-co-AM)等四种丙烯酰胺高分子絮凝剂. 用分子动力学方法,模拟计算了四种聚丙烯酰胺絮凝剂与氧化铝晶体(012)晶面的相互作用,以获得相应的形变能,结合能及理论排序,为阐释四种高分子絮凝剂的絮凝作用机理提供理论依据. 研究结果表明：四种聚合物分子相对Al₂O₃(012)面的初始位置均已贴近Al₂O₃(012)面,且絮凝剂分子中的O原子与Al₂O₃(012)面的Al原子之间存在强烈的相互作用;与Al₂O₃(012)晶面结合的高分子絮凝剂发生扭曲变形,但形变能远小于相应的非键作用能. Al₂O₃(012)晶面结合能的大小排序为P(DMB-co-AM)>P(OA-co-AM)>P(AA-co-AM)>P(AM), 显示四种絮凝剂中P(DMB-co-AM)的絮凝性能最佳,PAM絮凝效果最差.     

离子液体中AM/AMPS/N8AM三元共聚物的合成及溶液性能

以丙烯酰胺(AM)和2-丙烯酰胺基-2-甲基丙磺酸(AMPS)为亲水单体, 以N-辛基丙烯酰胺(N8AM)为疏水单体, 在离子液体[bmim]BF4中实现了疏水缔合丙烯酰胺三元共聚物的合成.     

高强度PAM/PVP半互穿网络凝胶制备及力学性能

以过硫酸铵为引发剂通过一步溶液聚合制备了由化学交联的聚丙烯酰胺(PAM)与聚乙烯吡咯烷酮(PVP)贯穿形成的PAM/PVP半互穿网络(semi-IPN)凝胶,着重研究了凝胶的机械性能。红外光谱、热重分析及拉伸实验分析可知PAM与PVP之间存在氢键作用。拉伸实验表明:在PAM中引入PVP,凝胶拉伸强度明显提高,m(PVP)/m(AM)=7.51%时制备的PAM/PVP semi-IPN凝胶拉伸强度比单纯化学交联的PAM增大64.67%;当AM=6mol/L,n(MBA)/n(AM)=1.67×10-4,m(PVP)/m(AM)=7.51%时,制备的凝胶机械性能较好,拉伸强度达到1.84MPa,断裂伸长率可达3322%;随着含水率增加,凝胶拉伸强度及断裂伸长率均有所降低。     

硫酸铵水溶液中分散聚合法制备两性共聚物P(AM-co-AA-co-DAC-co-DMC)

利用分散聚合技术,在硫酸铵水溶液中以丙烯酰胺(AM)、丙烯酸(AA)、丙烯酰氧乙基三甲基氯化铵(DAC)、甲基丙烯酰氧乙基三甲基氯化铵(DMC)为单体,合成了两性共聚物P(AM-co-AA-co-DAC-co-DMC).用FTIR,13C-NMR,TEM等方法表征了聚合物的结构和组成.考察了不同分散稳定剂、正负离子单体配比和pH对分散聚合的影响,并对P(AM-co-AA-co-DAC-co-DMC)水基分散聚合条件及稳定性进行了一些探讨.实验表明,在硫酸铵水溶液中制得较稳定的P(AM-co-AA-co-DAC-co-DMC)分散体系,应选用非离子型或阳离子型的分散稳定剂,如聚乙烯吡咯烷酮(PVP)、聚甲基丙烯酰氧乙基三甲基氯化铵(PDMC)、聚丙烯酰氧乙基三甲基氯化铵(PDAC),而其pH应在2到4之间.当选用占总质量1.5%的聚乙烯吡咯烷酮(PVP)为分散稳定剂,引发温度为40℃,正负离子单体物质的量比值大于1,pH=3时,可以制得总离子度超过25%的纳米级两性聚合物.     

Towards Control of Aggregational Behaviour of α-Lactalbumin at Acidic pH

α-Lactalbumin (α-La) undergoes considerable structural changes upon loss of bound Ca²⁺ at acidic pH, leaving α-La in a molten globule structure. Using fluorescence the present work provides more insight into the structural transition of α-La at acidic pH leading to protein aggregation, most likely caused by a combination of hydrophobic and electrostatic interactions. The rate of aggregation is determined by the protein concentration and temperature applied. Availability of Ca²⁺ stabilises the protein, and thus prevent aggregation at pH values as low as pH 2.9. In contrast, presence of Cu²⁺ induces a destabilisation of the protein, which can be explained by a binding to the Zn²⁺ binding site in α-La, possibly resulting in structural alterations of the protein. In general, presence of anions destabilise α-La at pH values below pI, with SO₄ ²⁻ exhibiting the strongest effect on the protein stability, thus correlating well with the Hofmeister series. At more acidic pH values far from pI, α-La becomes more stable towards ion induced aggregation, since higher ion activity is required to efficiently screen the charges on the protein surface. The results presented in this paper provide detailed knowledge on the external parameters leading to aggregation of α-La at acidic pH, thus permitting rational design of the aggregation process.     

电导法研究丙烯酰胺反相微乳液聚合体系的稳定性

制备了Span80-Tween80/异辛烷/AM-H2O反相微乳液体系,用电导法考察了不同HLB(亲水-亲油平衡)值下电导率的变化规律,并研究了正丁醇(n-butanol)、氯化钠(NaCl)和醋酸钠(NaAc)的加入对微乳液体系电导率变化的影响规律.实验表明:HLB值为5.4时体系的电导率变化较小.正丁醇质量浓度为25 g/L时电导率几乎没有变化,当NaCl质量浓度为50 g/L或NaAc质量浓度为25 g/L时可以增加体系的稳定性,为检测微乳液的稳定性提供了一种有效途径.     

Efficient,Simple Preparation of 1,3‐Diamine Derivatives through Addition of Acrylamides with Secondary Amines

Abstract

Reaction of acrylamides with secondary amines results in the formation of β‐amino‐propionamide through the addition reaction of N–H bond of amines across the double bond of acrylamides in the good to excellent yield. The structure of 2‐methyl‐3‐(1‐piperidinyl)‐propionamide has been determined by X‐ray analysis.     

An eco-friendly synthesis,characterization and antibacterial applications of novel almond gum – poly(acrylamide) based hydrogel silver nanocomposite

Polysaccharide based semi interpenetrating hydrogel (SIH) networks of cross-linked poly(acrylamide) was synthesised through an redox initiating free radical polymerization utilizing almond gum as a grafting backbone, N,N′– methylenebisacrylamide (MBA) as the cross-linker and ammonium persulphate (APS) – N,N,N′,N′-tetramethyl ethylenediamine (TEMED) as the redox initiator pair. Silver ions were introduced into the hydrogel matrix and silver nanoparticles of invariable size were developed insitu of the swollen hydrogel by the reduction of silver ions (Ag⁺) using azadirachta indica (neem) leaf extract. The prepared hydrogel - silver nanocomposite (HSN) was characterized by UV–visible diffused reflectance spectroscopy (DRS), fourier transform infrared spectroscopy (FT-IR), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis (EDX) and thermogravimetric analysis (TGA). The influence of pH on the swelling behavior of HSN was studied and the antibacterial activity of the developed nanocomposite was evaluated.     

Evaluation of electroosmotic markers in aqueous and nonaqueous capillary electrophoresis

The most common method to determine the EOF in CE is to measure the migration time for a neutral marker. In this study, 12 compounds (three novel and some previously used) were investigated as EOF markers in aqueous and nonaqueous BGEs. In the aqueous buffer systems (ammonium acetate, sodium phosphate, and sodium borate) the evaluation included a wide pH range (2–12). Two BGEs contained chiral selectors (sulphated‐β‐CD, (?)‐diketogulonic acid) and one that contained a micellar agent (SDS) were included in the study. The majority of the evaluated compounds were found to migrate with the EOF in the water‐based BGEs and are thus useful as EOF markers. However, in the SDS‐based BGE only four of the compounds (acetone, acrylamide, DMSO, and ethanol) were found to be applicable. In the nonaqueous BGEs 11 markers (acetone, acetophenone, acrylamide, anthracene, benzene, 4‐(4‐methoxybenzylamino)‐7‐nitro‐2,1,3‐benzoxadiazole, benzyl alcohol, 2,5‐diphenyloxazole, ethanol, flavone, and mesityl oxide) seemed to be functional as EOF markers. Even though several of the evaluated compounds can be used as EOF markers in the investigated BGEs, the authors would recommend the use of acrylamide as a general marker for UV detection. Furthermore, the four fluorescent markers (of which three were novel) gave RSD values equal to the other markers and can be used for the determination of the EOF in CE or microchip CE with fluorescence detection.