对称长链和近对称短链两嵌段聚合物混合体系相行为研究

利用自洽平均场理论(SCMFT)系统地研究了对称长链和近对称短链两嵌段聚合物混合体系在纳米尺度下的自组装行为.体系中具有较高聚合度的对称长链熔体处于层状相,聚合度较低的近对称短链熔体处于无序相,而其混合体系却随着两种成分的不同比例呈现出有序-无序相转变、有序-有序相转变及有序-无序两相共存等复杂的相行为,计算结果与近期类似体系的实验有着较好的吻合.同时与两种对称的两嵌段聚合物混合体系的计算结果进行了比较,得出这两种体系的异同之处.     

在平行板受限条件下AB两嵌段共聚物/纳米粒子复合物自组装行为的Monte Carlo模拟

采用Monte Carlo模拟方法研究了在平行板受限条件下A_(15)B_5非对称两嵌段共聚物与纳米粒子复合物的自组装行为,其中平行板对多组分嵌段A具有吸引相互作用.模拟结果表明,纳米粒子在两嵌段共聚物/纳米粒子复合物中的体积分数、嵌段共聚物不同嵌段与纳米粒子间的相互作用均对体系在平行板受限条件下的形貌结构及纳米粒子在体系中的分布有重要影响.当平行板间距一定时,未添加纳米粒子的A_(15)B_5非对称两嵌段共聚物中的A嵌段被吸附在平行板上形成层状相,而B嵌段则在平行板中形成六角堆积穿孔层状结构.加入与A嵌段不相容而与B嵌段相容的纳米粒子后,增加了纳米粒子与B嵌段的相容性,有利于保持B嵌段所形成的穿孔结构及孔洞尺寸,同时纳米粒子能够均匀地分散在B相区中.当引入的纳米粒子与A和B两嵌段均不相容时,降低纳米粒子与嵌段共聚物的不相容性同样有利于维持体系的穿孔结构.当纳米粒子与AB两嵌段共聚物间的排斥作用微弱时,即使含量较高,纳米粒子也不聚集,并且均匀分布在A相区与B相区的交界处.     

嵌段共聚物和星型均聚物共混体系相行为的自洽场理论研究

用自洽场理论方法(Self-consistent field theory, SCFT)计算了嵌段共聚物AB和三等臂星型均聚物A共混体系的微相形态. 为了简化计算, 着重讨论了固定嵌段共聚物本体的相形态(如层状相)时, 所加入的均聚物的体积分数及均聚物与嵌段共聚物链长之比对体系相形态的影响; 并结合体系的熵和相互作用能的变化, 讨论了星型均聚物在体系微相结构中的分布.     

La—LaCl3—KCl熔体的计算机模拟研究

用Monte Carlo方法对La-LaCl_3-KC1体系在1223K时的结构进行了计算机模拟研究,得到了熔体中诸离子对的偏径向分布函数和体系在1223K的势能和内能。结果表明,在熔体中La(Ⅲ)有相当一部分以LaCl_6~3六配位形式存在,而La(Ⅱ)则主要以LaCl_4~2四配位形式存在。结果还表明,熔体中的自由体积分布不均匀,存在许多不规则的空孔和缝隙,其中XK~+·YC1~-集团内的缝隙比纯KC1熔体中的缝隙明显增多。     

两亲性/双疏性嵌段共聚物共混体系的自组装行为研究

采用耗散粒子动力学方法,研究了两亲性嵌段共聚物和双疏性嵌段共聚物共混体系的自组装行为,探讨了双疏性嵌段共聚物的浓度以及双疏性嵌段共聚物的嵌段体积分数对聚集体结构的影响.结果表明,随着双疏性嵌段共聚物浓度的增加,聚集体发生自囊泡到棒状胶束再到同心圆多舱胶束的转变,且当浓度较高时,同心圆多舱胶束的同心圆层数量与浓度密切相关.当双疏性嵌段共聚物中的嵌段体积分数降低时,球形胶束由同心圆结构转变为非同心圆结构.此外,利用Minkowski泛函方法表征了多舱胶束的形成过程,发现这是一个先形成大尺度球形结构、再形成小尺度内核结构的分级组装过程.     

棒-棒二嵌段共聚物自组装行为的自洽场研究

利用格子自洽场模型, 模拟了棒-棒二嵌段共聚物熔体系统的自组装行为, 并与线-棒二嵌段共聚物系统性质进行了对比. 结果表明, 棒-棒二嵌段共聚物系统的有序无序转变临界点低于线-棒二嵌段共聚物系统的相变临界点. 通过模拟计算, 发现薄层交叠柱状相、柱状相、层状相和Z形层状相4种稳定的有序形貌. 薄层交叠柱状相和柱状相仅在有序无序转变曲线的边缘位置出现, 层状相也仅存在于有序无序转变临界点上面的一小块区域内, 而稳定的Z形层状结构则占据了相图中较强相互作用的大部分区域.     

从溶胀平衡研究玻璃态高聚物的凝聚缠结网络

在13~15℃室温条件下对聚苯乙烯(PS)颗粒在二氧六环/水混合溶剂中的溶胀情况进行目视观察,可以看到,当减小混合溶剂二氧六环/水中的水含量时,PS颗粒从玻璃态到溶胀的玻璃态、溶胀的高弹态、流体态的转变,与PS颗粒升温时从玻璃态到高弹态、流体态的转变相对应.选定混合溶剂二氧六环/水(水6·8wt%)对一个单分散PS试样(Mw=1·68×105)在30℃进行分相平衡和溶胀平衡的测定.分相平衡是先将PS/二氧六环/水(混合溶剂水含量6·8wt%)体系加热到130℃使PS溶解成一均相溶液,然后在冷却过程中分相,在30℃达分相平衡(30天)时,浓相高分子体积浓度p″=0·304,稀相几乎为纯溶剂.从Flory-Huggins相平衡理论得出此体系的高分子-溶剂相互作用参数χ=0·63.本工作使用的单分散PS试样在选定的混合溶剂,即二氧六环/水(水6·8wt%)中,30℃时不能溶解只能溶胀,单分散PS颗粒淬冷试样(密度ρp=1·0451g/mL)到达溶胀平衡(80天)时浓相高分子体积浓度p″=0·308.而此淬冷试样经在80℃热处理100h后的老化试样(ρp=1·0470g/mL)达溶胀平衡(70天)时p″=0·312.从溶胀过程中浓相体积变化曲线可知试样经在80℃热处理过程中凝聚网络趋向于更均一,更接近热处理温度下的平衡态,试样密度增大,网络产生了新的链间凝聚,物理交联密度增大(凝聚点间分子量减小).从溶胀平衡理论并取χ=0·63(分相平衡)可得到淬冷试样的物理交联点间分子量Mc=11·6×104,老化试样的物理交联点间分子量Mc=6·9×104.实验结果说明溶胀过程及溶胀平衡的测定可以反映玻璃态高聚物中的凝聚网络结构的细节,而且非常敏感.     

锂—碳体系的研究

用热分析法研究了锂-碳体系.制备熔体和记录冷却曲线是在氩气氛中进行的. 确定了体系在锂和所生成的碳化锂(Li_2C_2)之间这一部分的状态图.锂和碳化锂形成低共熔体,低共熔体的组成靠近纯锂(合碳少于1原子%),其熔点为165°. 用沸点法测定了纯锂以及含碳少于15克原子%的熔体在790-950°的蒸气压.根据蒸气压的等压线确定了在较高温度范围内的液相线. 碳化锂被水完全分解,放出当量体积的乙炔,并无自由态的碳及其他物质残留. 热分析及Debye-Scherrer法的结果指出:碳化锂有几种变体,转化温度约在410°,440°和560°.     

多嵌段共聚物/纳米粒子杂化多级结构的光学性能

结合耗散粒子动力学模拟和时域有限差分方法,研究了A(BC)_n多嵌段共聚物和纳米粒子共混体系的自组装行为及其光学性能,分析了纳米粒子体积分数和嵌段间相互作用强度对自组装形貌及其光学性能的影响。结果表明,A(BC)_n多嵌段共聚物/纳米粒子共混体系可形成有机/无机杂化的多级结构,改变纳米粒子的体积分数和嵌段间相互作用强度可以调控纳米粒子的分布及其相应的多级结构。不同尺度的结构对不同频率光的反射作用有明显区别,而纳米粒子的加入显著增大了反射峰的强度和宽度。改变纳米粒子的分布可调控反射峰的强度和宽度。     

基于甲壳型液晶高分子的刚-柔型二嵌段共聚物的层状相:链伸展行为的研究

研究了一系列以聚己内酯(PCL)为柔性链段、甲壳型液晶高分子聚{2,5-二[(4-甲氧基苯基)氧羰基]苯乙烯}(PMPCS)为刚性链段的刚-柔型二嵌段共聚物(PCL-b-PMPCS)的微相分离结构.小角X射线散射(SAXS)和广角X射线衍射(WAXD)实验结果表明,当PMPCS为无定形态时,PCL-b-PMPCS的微相分离行为与柔-柔型二嵌段共聚物相似,其相形态主要取决于两段的体积分数.随温度升高,PMPCS链段采取伸展的棒状构象,形成六方柱状向列相(ΦHN),会诱导体系的微相分离结构出现"有序-有序"或"无序-有序"转变,使得在很宽的PMPCS体积分数(fPMPCS:40%~80%)内样品均呈现层状微相分离结构.我们对在200oC得到的层状相SAXS数据进行了一维相关函数分析,详细考察了层状相中PMPCS及PCL相区的厚度(LPMPCS、LPCL)与相应链段聚合度(NPMPCS、NPCL)的关系.对PMPCS相区,发现LPMPCS=0.2NPMPCS(nm).因棒状PMPCS链段与层的法线方向平行,该线性关系表明PCL-b-PMPCS的层状相为"单层近晶A相"结构,LPMPCS即为棒状PMPCS链段的长度,可通过控制PMPCS的聚合度予以精确控制.对PCL相区,则LPCL与NPCL近似有标度关系LPCL~NPCL0.85,说明处于熔融态的PCL链段受迫强烈伸展.进一步分析WAXD实验数据并计算每根PMPCS链段在层状相中的界面面积(S/X)可知,随NPMPS增大,PMPCS链段的液晶度从~20%增至~55%,S/X则从~2.4nm2增至~2.7 nm2.与此相应,PCL链段的伸展程度会略有降低,说明LPCL有较弱的NPMPCS依赖性.另一方面,LPCL与S/X的乘积与NPCL满足线性关系LPCL(S/X)=0.21NPCL(nm3),斜率即为PCL重复单元的体积.     

聚赖氨酸为主链的牙刷状分子刷的可控合成

设计合成了溴基功能化的赖氨酸单体(Br-lys)并通过关环反应制备了对应的溴代L-赖氨酸N-羧酸酐(Br-Lys-NCA)单体.利用过渡金属引发剂Ni(COD)depe调控的NCA活性开环聚合和顺序添加单体的方法,得到了组成和结构明确的聚(ε苄氧羰基L-赖氨酸)-b-PBrLL(PZLL-PBrLL)两嵌段共聚肽.利用PZLL-b-PBrLL两嵌段共聚肽为大分子引发剂,通过ATRP引发甲基丙烯酸寡聚乙二醇酯(EGMA),合成了以聚赖氨酸为骨架的牙刷状分子刷.研究发现PZLL-PBrLL两嵌段在四氢呋喃中形成α-螺旋结构,螺旋度随着PBrLL链段的增长而降低,而PZLL-b-(PBrLL-g-PEGMA)形成部分α-螺旋构象,螺旋度随侧链PEGMA增长而减小.     

苯乙烯-2-乙烯基吡啶两嵌段共聚物的合成与表征

采用阴离子聚合技术合成了一系列苯乙烯 ２ 乙烯基吡啶的两嵌段共聚物（ＰＳ ｂ Ｐ２ＶＰ），并采用ＧＰＣ、ＦＴＩＲ、ＮＭＲ（１Ｈ ＮＭＲ和１３Ｃ ＮＭＲ）、ＤＭＡ等手段进行了表征．结果表明，产物为高分子量、窄分布的两嵌段共聚物，具有微相分离的两相结构     

单体组成对甲基丙烯酸甲酯/丙烯酸丁酯RAFT共聚合转移常数的影响

采用Z基团为—CH2C6H5的RAFT试剂为链转移剂,AIBN为引发剂,60℃下进行甲基丙烯酸甲酯/丙烯酸丁酯(MMA/BA)的本体RAFT共聚合,并用GPC法测算不同单体组成下低聚物RAFT的链转移常数(Ctr).实验表明,对BA的均聚合,Ctr高达116,但对MMA的均聚合,Ctr约为0.1.在共聚体系中,Ctr与fMMA之间为非线性关系,随着fMMA的增加呈下降趋势.Ctr随单体组成的变化规律可以很好地解释不同单体组成下RAFT共聚合中分子量及其分布随转化率变化的规律.     

Cononsolvency-induced micellization of pyrene end-labeled diblock copolymers of N-isopropylacrylamide and oligo(ethylene glycol) methyl ether methacrylate

Pyrene end-labeled double hydrophilic diblock copolymers, poly(N-isopropylacrylamide)-b-poly(oligo(ethylene glycol) methyl ether methacrylate) (Py-PNIPAM-b-POEGMA), were synthesized via consecutive reversible addition-fragmentation chain transfer polymerization using a pyrene-containing dithioester as the chain transfer agent. These diblock copolymers molecularly dissolve in pure methanol and water, but form well-defined and nearly monodisperse PNIPAM-core micelles in an appropriate mixture of them due to the cononsolvency of PNIPAM block. 1H NMR, laser light scattering, fluorescence spectroscopy, and transmission electron microscopy were employed to characterize the cononsolvency-induced PNIPAM-core micelles. When the volume fraction of water, phi water, in the methanol/water mixture is in the range of 0.5-0.8, the sizes of micelles are in the range of 20-30 nm in radius for Py-PNIPAM50-b- POEGMA18. At phi water = 0.5, the formed micelles possess the highest overall micelle density and the largest molar mass. The effects of varying the block lengths of Py-PNIPAM-b-POEGMA diblock copolymers on the structural parameters of PNIPAM-core micelles have also been explored. Although we can observe the immediate appearance of bluish tinge upon mixing the diblock copolymer solution in methanol with equal volume of water (phi water = 0.5), which is characteristic of the formation of micellar aggregates, the whole micellization process apparently takes a relatively long time to complete, as revealed by monitoring the time dependence of fluorescence emission spectra. The excimer/monomer fluorescence intensity ratios, IE/IM, continuously decrease with time and then reach a plateau value after approximately 20 min. The decrease of IE/IM after the initial formation of pseudo-equilibrium micelles should be ascribed to the structural rearrangement and further packing of PNIPAM segments within the micelle core, restricting the mobility of pyrene end groups and decreasing the probability of contact between them. Compared to the conventional cosolvent approach employed for the micellization of block copolymers in selective solvents, the reported cononsolvency-induced unimer-micelle-unimer transition of Py-PNIPAM-b-POEGMA in methanol/water mixtures has been unprecedented.     

Permeability of heterogeneous gels

Gels made by radical copolymerization of monofunctional and difunctional monomer units in the presence of swelling medium will tend to be heterogeneous. A case in point is acrylamide co-polymerized with N,N′-methylene bis-acrylamide in water. Such gels can be assumed to be two-phasic with both phases gels, but of different average concentration and average degree of cross-linking. As Weiss and Silberberg have shown, permeability can be used to characterize the distribution in space. In this paper, their earlier model is expanded and improved by considering specifically the permeability of each of the two phases and taking into account that each of these phases separately must have come into swelling equilibrium with the swelling medium, water. It can be shown that only the length of the Kuhn statistical element remains as a free parameter in this model. Essentially the same value of this parameter, however, accurately accounts for the measured permeability. It is found that at an overall volume fraction of about 0.16, the two-phase structure tends to disappear. For higher degrees of crosslinking, this occurs because the more dilute phase takes over the entire space; for more lightly crosslinked systems, the more concentrated phase takes over. The heterogeneity of the distribution lies in the nanometer range and reasonable agreement between the results obtainable from permeability and from viscoelasticity can be demonstrated. These results are consistent with the model for the polymerization process.     

Synthesis and characterization of shell-cross-linked polymer networks and large-core star polymers: Effect of the volume of the cross-linking mixture

Group transfer polymerization and sequential addition of monomer and cross-linker were employed for the preparation of two new polymer structures, one of a polymer network and the other of a star polymer. The synthesis was completed in two steps, involving the synthesis of linear methyl methacrylate (MMA) arms of degree of polymerization of 20, followed by their cross-linking using a mixture of MMA monomer and ethylene glycol dimethacrylate (EGDMA) cross-linker. In this study, the volume of the cross-linking mixture was varied systematically. Furthermore, two mixture compositions were employed, involving MMA:EGDMA molar ratios of 1:1 and 3:1, leading to two series of polymeric materials. It was found that at a given cross-linking mixture composition, a larger volume of the cross-linking mixture favored the formation of polymer networks, whereas a smaller volume favored the formation of star polymers. The linear precursors, the star polymers and the extractables from the polymer networks were characterized by gel permeation chromatography in tetrahydrofuran (THF). The absolute weight-average molecular weight, the number of arms and the hydrodynamic radii of the star polymers, as determined using static and dynamic light scattering in THF, respectively, and their average radii as determined by atomic force microscopy, increased as the volume of the cross-linking mixture increased. The gravimetrically measured degrees of swelling in THF, the network sol fraction and the percentage of branched polymer in the sol fraction decreased as the volume of the cross-linking mixture increased.     

聚对苯二甲酸乙二酯缩聚反应分子量再分布

<正> 本文研究了聚对苯二甲酸乙二酯(PET)的分级结晶现象,结果另文报道。在研究中发现,当高分子量PET组分中加入低分子量PET组分时,表现出十分不同的熔融行为,但在230℃以上长时间等温热处理以后,又恢复高分子量PET的熔融行为。认为,在高温下,具有不同初始分子量分布的两个组分发生了缩聚反应,使分子量重新分布,失去了原来两种不同分子量分布的特征。     

沉淀聚合制备聚(季戊四醇三丙烯酸酯-苯乙烯)单分散微球及其形成机理

以季戊四醇三丙烯酸酯(PETA)作交联剂,苯乙烯作共聚单体,偶氮二异丁腈作引发剂,在乙醇或其与水的混合溶剂中沉淀聚合制备了交联聚合物微球.研究了反应时间、交联剂用量以及溶剂中水含量对聚合过程及微球的影响.结果表明当PETA用量在单体质量的5%-35%之间且反应时间不低于6h时可制得单分散聚合物微球.当PETA用量低于20%时,所得微球的粒径随PETA用量的增加逐渐减小,粒径分布逐渐变窄;此后继续提高PETA用量,微球粒径又逐渐增大,粒径分布逐渐变宽.向反应介质中加入水,可明显提高微球产率及单体转化率,但其体积分数达30%时,所得微球分散性变宽.在此基础上对微球的形成机理也进行了讨论.     

PE/PEO/PE-PEO 对称三元共混体系相行为的耗散粒子动力学模拟研究

建立了对应实验体系聚乙烯/聚氧化乙烯/聚乙烯-聚氧化乙烯嵌段共聚物(PE/PEO/PE-PEO)的对称三元共混模型,并采用耗散粒子动力学(DPD)模拟方法对其相行为进行了理论研究.研究结果表明,随着均聚物体积分数的增加,体系的平衡相态发生由层状相(LAM)到双连续微乳液(BME)再到相分离(PS)的转变,相态演化规律和...     

丙烯酸全氟烷基乙基酯嵌段共聚物的组成结构表征

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