BM-DVB多孔共聚体及其炭化物的热性能

在相同条件下,分别以4,4'-双马来酰亚胺二苯基甲烷(BM)与二乙烯基苯(DVB)的摩尔配比1∶4、1∶1、4∶1,采用悬浮共聚法合成了BM-DVB珠状多孔共聚体.炭化前,对所制BM-DVB共聚体用二种方法进行预处理:(1)热空气稳定化(产物标名PO-C 800);(2)H3PO4浸渍(产物标名P 800).而后,将两种预处理所获产物在Ar气中800℃进行炭化.采用热重(TG)和热差(DSC)法表征了BM-DVB多孔共聚体及其炭化物的热性征.结果表明:单体配比的差异导致了初始聚合体的不同交链程度.共聚体及其炭化物的热稳定性与其组成存在一定的相关性.在BM:DVB摩尔比为4∶1时,BM-DVB共聚体的耐热性最高;其因在于共聚体中含有的氮原子浓度最高.在BM:DVB摩尔比为1∶4时,BM-DVB共聚体具有高的交链度,但热性能最差;这可能由其微孔性能和较少的含氮量所致.而它们炭化物的热性能却非常相似,几乎不受BM-DVB共聚体的影响.可以认为,影响BM-DVB炭化物热性能更重要因素是BM-DVB共聚体在预处理过程中形成的孔隙率和表面化学性能.     

Carbon anode materials based on copolymers of nitrogen-containing monomers with DVB

Through the measurement of electrochemical properties of carbon anodes based on copolymers of 4-VP and AN with crosslinker DVB, it is found that the introduction of crosslinker DVB can favor the enhancement of reversible capacity, and the highest can be up to 600 mAh g^{– 1}. Measurements of Thermal gravity analysis, elemental analysis, X-ray powder diffraction, scanning electron microscopy and specific surface area indicate that the incorporation of DVB into polymer PAN can not only affect the contents of nitrogen and hydrogen, but also favor the carbonization process. In addition, it can result in improvement of the regularity of the obtained carbon structure, i.e. the formation of graphite structure, and the number of micropores is increased. By virtue of all these factors, charge capacity below and above 0.9 V enhances and charging voltages decrease with the addition amount of DVB.     

Thermal Degradation Studies on Polyaniline–Polypyrrole Copolymers Prepared by Microemulsion Methods

Solvent- and water-based microemulsions of aniline and pyrrole copolymers were synthesized, and the thermal degradation properties of the copolymers were studied. The morphology of the copolymers prepared using solvent-based microemulsions containing 80 % aniline in the feed showed highly oriented, crystalline, ordered long nano-fibers which were even more structured than that of pure aniline prepared by the same method. The influence of the degree of crystallinity calculated from X-ray diffraction and morphology had an overlap with thermal degradation and activation energies of different transitions. Copolymers prepared with water-based microemulsions were thermally less stable than the ones prepared using solvent-based microemulsions. The concentration of pyrrole and aniline mutually influenced the thermal properties of the copolymers.     

偏氯乙烯-丙烯腈悬浮共聚物的热行为与结晶度

用DSC法研究了VDC－AN悬浮共聚物的玻璃化转变和热熔融行为,并用Barton方程定量关联了Tg与组成的关系,用TGA法研究了共聚物的热分解行为,结果表明,AN单元对与其相邻连拉的VDC单元脱HC1有诱导催化作用,由DCS法和X射线衍射法得到高VDC含量的共聚物结晶度与AN含量成线性关系,而在高AN含量时则与AN组成成三次多项式关系。     

导电性微纳米结构N-乙基苯胺/苯胺共聚物的静态合成

以N-乙基苯胺（NA）、苯胺（AN）为单体,过硫酸铵（APS）为引发剂,通过静态聚合法制备了导电性微纳米结构N-乙基苯胺-苯胺共聚物（PNAAN）。结果表明,共聚物的形貌、结构和性能强烈依赖于NA/AN物质的量比和APS/单体物质的量比。APS/单体物质的量比为1.0时,PNAAN（10∶90）共聚物为直径139 nm...     

添加正十八烷微胶囊的丙烯腈与甲基丙烯酸甲酯共聚物的合成与表征

采用氧化还原引发剂合成了含有正十八烷微胶囊的丙烯腈/甲基丙烯酸甲酯共聚物。测试表明,丙烯腈和甲基丙烯酸甲酯单体发生了共聚,共聚物中丙烯腈成分的实测含量略低于理论含量;试样中的微胶囊的吸热和放热温度与纯微胶囊的吸热放热温度接近,随着微胶囊含量的增加,共聚物中微胶囊的热效率逐渐增大;随着微胶囊含量的增加,试样中共聚物的结晶度增大。     

Preparation of a hyperbranched polycarbosilane precursor to SiC ceramics following an efficient room-temperature cross-linking process

Room-temperature cross-linking of a hyperbranched polycarbosilane (HBPCS) with divinylbenzene (DVB) in the presence of the cyclohexanone peroxide–cobaltous naphthenate (CHP–CN) initiator system was studied. According to the Fourier transform infrared spectroscopy (FT-IR) and ¹H nuclear magnetic resonance (¹H NMR) results, the cross-linking reaction occurred via the vinyl polymerization. The GPC analysis confirmed the molecular weight of the cross-linked HBPCS significantly increased. Thermal behaviors of cross-linked HBPCS and original HBPCS were investigated by thermal gravimetric analysis-differential thermal analysis (TGA–DTA). The TGA results indicated that the ceramic yield of HBPCS remarkably increased by the cross-linking treatment. For the HBPCS/10 wt% DVB system, the maximum of reaction degree of HBPCS was obtained, which might be responsible for the highest ceramic yield of 70.1 wt% at 1000 °C. However, the ceramic yield of the non-crosslinked HBPCS was only 45 wt% at 1000 °C. The evolution of crystal structure of SiC as a function of pyrolysis temperature was traced by means of X-ray diffraction (XRD) and FT-IR. With the pyrolysis temperature increasing, the β-SiC peaks became sharper and the grain size also grew larger. As the DVB content increased, the intensity of β-SiC peaks significantly reduced, indicating smaller β-SiC grain size.     

The effect of transient proanthocyanidins preconditioning on the cross-linking and mechanical properties of demineralized dentin

Proanthocyanidin-based preconditioners were prepared by adding powdered proanthocyanidins-rich grape seed extract to various solvents at different concentrations. Demineralized dentin specimens were preconditioned for 20, 30, 60 or 120 s, followed by the evaluation of their cross-linking degree, mechanical properties and micromorphology. The cross-linking degree of the demineralized dentin collagen exhibited concentration- and time- dependent increase after preconditioning treatment, irrespective of the preconditioner and the solvent. When treated for the same exposure time, specimens after 15% proanthocyanidins preconditioning resulted in the highest mean ultimate tensile strength compared with all the other groups tested. Five percent glutaraldehyde control group produced the highest cross-linking degree, but the ultimate tensile strength was lower than that of 15% proanthocyanidins group. The field emission scanning electron microscopy confirmed that the demineralized dentin collagen was in a homogeneous and regular arrangement after preconditioning and maintained expanding, regardless of the surface moisture conditions.     

聚丙烯酸酯-纳米二氧化硅接枝复合胶粒在熔融剪切场中的取向重排

以聚丙烯酸酯-硅烷改性二氧化硅（PAcr-MPS-SiO₂）石榴状接枝复合胶粒为分散相,以聚甲基丙烯酸甲酯树脂（PMMA）为连续相,在HAKKA转矩流变仪中进行熔融共混,考察不同交联结构复合胶粒在不同熔融共混条件下的剪切形变行为。发现:微米级复合胶粒在熔融共混过程中既受强力剪切场的诱导作用,同时又受复合胶粒接枝交联结构的约束作用,因而依次会经历球形、椭球形、棒状、微纤状等取向形态,但又不至于出现大规模的撕裂解离现象,从而可在聚合物基体中原位并排生成大量具有较大长径比的微纤状取向结构体。通过改变SiO₂表面MPS改性程度和SiO₂含量调节复合胶粒的交联程度,或通过改变螺杆转速调节熔融剪切场的剪切强度,可在一定范围内调控复合胶粒及其中的接枝SiO₂粒子簇的取向程度。其中,当胶粒凝胶率为40%、共混温度180℃、螺杆转速65 r/min、共混时间12 min时,可得到平均长径比达到11.8的规则并排取向结构。研究可为聚合物基体中原位构建和有效调控一维取向结构提供一种新途径。      

不同分子量丙烯腈-丙烯酰胺共聚物溶液的流变性研究

将不同分子量的丙烯腈（AN）与丙烯酰胺（AM）的共聚物溶解于二甲亚砜（DMSO）中，获得聚丙烯腈（PAN）溶液。采用旋转粘度计和锥板流变仪，从非牛顿指数n、流动活化能△Eq、结构粘度指数△ηa和弹性模量G等方面比较了不同分子量PAN溶液的流变性能。结果表明，分子量高的PAN溶液的表观粘度对应力变化敏感，分子理低的PAN溶液的表现粘度对温度的变化敏感，无论是从粘性还是从弹性角度看，低分子量PAN溶液的物理稳定性好。     

壳聚糖-聚乳酸接枝共聚物的制备与表征

将醛基化改性的聚乳酸接枝到壳聚糖,并通过元素分析、红外光谱(IR)、核磁共振(1H-NMR)、X射线衍射(XRD)和热重分析(TG)分别对接枝产物的接枝率、结构和结晶性能进行表征。IR和1H-NMR结果表明聚乳酸成功接枝到壳聚糖主链,不同投料比和接枝率的关系与元素分析一致;PLLA-CHO/CS-NH2最佳摩尔比为1∶2.5,此时的接枝率为52.22%;XRD和TG结果表明接枝产物的结晶度和热分解温度降低,说明壳聚糖的高结晶性得到改善,其应用范围扩大。     

交联剂对可膨胀小球制备的影响

以丙烯腈为主要单体,以氢氧化镁为无机分散剂,采用常压聚合法,制备了膨胀倍率达到20-30倍的可膨胀小球。系统研究了二丙二醇二丙烯酸酯(DPGDA)、三缩丙二醇二丙烯酸酯(TPGDA)、新戊二醇二丙烯酸酯(NPGDA)、三羟甲基丙烷三丙烯酸酯(TMPTA)和二乙烯基苯(DVB)等5种交联单体对可膨胀小球制备的影响。通过扫描电子显微镜、热重分析、交联密度测定等手段研究了可膨胀小球的形貌、粒径、发泡剂的含量、交联密度、发泡倍率。确定DPGDA为最佳的交联剂种类,用量为1.7%。采用DPGDA作为交联剂的小球既具有较完好的球状形貌,又有较小的粒径,较高的发泡剂含量和较高的交联度,膨胀倍率可达30倍。     

The incorporation of polar monomers in copolymers based on styrene and divinylbenzene obtained from glycerol suspension polymerization

Porous copolymer networks based on styrene (STY) and divinylbenzene (DVB) containing polar monomer (methacrylamide — MAM, methacrylic acid — MAA or acrylonitrile — ACN) were prepared by suspension polymerization using glycerol as a dispersant medium. Poly(styrene-co-methacrylamide-co-divinylbenzene), poly(styrene-co-methacrylic acid-co-divinylbenzene) and poly(styrene-co-acrylonitrile-co-divinylbenzene) were synthesized using mixtures of toluene with 2-butanone, toluene and 2-butanone and n-heptane with ethylacetate, respectively at different dilutions: 50%, 100% and 120% (v/v). The copolymers were characterized by bulk density, infrared spectrometry (FTIR) and elemental analysis (CHN). Morphological features of the copolymer pearls were evaluated by microscopic analysis and correlations between porous structure and parameters of reaction were found. The copolymers presented high incorporation of polar monomers. The pearl porosities and visual appearances had a strict relation with the monomer type and the dilution degree employed in synthesizing them.     

聚合温度对丙烯腈/丙烯酸甲酯共聚物结构与性能的影响

在不同聚合温度下,以水相沉淀聚合法合成了丙烯腈与丙烯酸甲酯共聚物。采用差示扫描量热分析(DSC)、元素分析(EA)、核磁共振波谱分析(NMR)等方法对聚合物的组成和结构进行了表征。结果表明,不同的聚合温度对丙烯腈与丙烯酸甲酯共聚物的热力学行为、组成及序列长度产生一定的影响。相同的单体投料比,随着聚合温度的升高,共聚物中丙烯腈的摩尔含量降低,丙烯腈的数均序列长度减小。     

炭纤维前驱体丙烯腈-丙烯酰胺共聚物研究

以二甲基亚砜为溶剂,偶氮二异丁腈为引发剂,用溶液聚合法合成了炭纤维用丙烯腈(AN)-丙烯酰胺(AM)共聚物.低转化率下,测得单体竞聚率,讨论了聚合机理模型.采用统计方法,推测了不同转化率下AN与少量AM(AM的摩尔分数＜5%)共聚物的微观结构.结果表明,在该聚合体系中,AN、AM的竞聚率值分别为r(AN)=0.46,r(AM)=0.01;AN与AM聚合机理为末端基终止模型;AM的引入降低了AN单元的数均序列长度;随着转化率的提高,链段分布逐渐变宽,AN长序列单元逐渐增加.     

Synthesis of oriented hydroxyapatite crystals: Effect of reaction conditions in the presence or absence of silk sericin

The purpose of this study was to investigate the effect of silk sericin (SS) on the morphology and crystallinity of hydroxyapatite (HAp) crystals synthesized at the pH 7.4-12 and 50 °C via a biomimetic method. Using X-ray diffraction (XRD), transmission electron microscope (TEM) and high-resolution transmission electron microscope (HRTEM), it was revealed that a homogeneous assembly could be obtained in the presence of SS, which held a highly ordered microstructure and poor crystallinity. But in the absence of SS, an oriented aggregate could be prepared at 50 °C and pH 10, which held more confused crystal lattice lines. The results proved that the biomimetic structure of HAp could be constructed under the controlled reaction conditions, which may offer a new clue on the understanding of the process of biomineralization.     

共聚聚丙烯的交联作用对材料断裂行为的影响

采用固定引发剂(DCP)及助交联剂(DVB)配比,增加DCP/DVB用量对聚丙烯(PP)材料进行交联改性,利用EWF方法评价了材料断裂行为,并探讨了结构变化对断裂性能的影响。研究表明,不同DCP/DVB改性剂用量对PP链结构及断裂行为产生较大的影响,改性剂的加入有利于交联结构等的形成,进而限制分子链间或晶粒间的相互移动;交联结构较少时,材料的比基本断裂功We值减小,比非基本断裂功βWp有所增加;而当交联结构较多时,We值有所回升,βWp有所降低。     

Bisphenol A imprinted polymer adsorbents with selective recognition and binding characteristics

Imprinted copolymers, which highly recognized and bound bisphenol A (Bis A), were synthesized by using covalent imprinting technique. Bisphenol A dimethacrylate (BADM) was used as a template monomer in the copolymerization with a crosslinkable monomer of divinyl benzene (DVB), ethylene glycol dimethacrylate (EGDM) or N,N’-methylenebisacrylamide (MBAA). The resultant copolymer was hydrolyzed in acidic or basic condition. It was found that the Bis A imprinted copolymers of EGDM and MBAA had no selectivity to Bis A, because the crosslinker dissociated by the hydrolysis reaction and thus comprehensive imprinted sites were not formed. On the other hand, imprinted copolymer of DVB showed excellent selectivity to differentiate Bis A from bisphenol E and bisphenol F (Bis F). Characterization of the copolymers suggested that the DVB copolymer had resistance to the acid and alkali conditions. Effect of recognition by the Bis F imprinted polymer was also compared with that of the Bis A imprinted polymer, when DVB and bisphenol F dimethacrylate were copolymerized. The Bis F imprinted copolymer was able to recognize Bis F in ethanol solution, however showed higher binding capacity for both Bis A and Bis F in water solution without recognition. Therefore, hydrophobic interaction between Bis A and the imprinted site enhanced the binding capacity with high selectively for the BADM-co-DVB imprinted copolymer.     

Preparation of highly cross-linked monodispersed functional polystyrene particles by utilizing the delayed addition method

A facile and effective method was successfully developed to prepare the highly cross-linked monodispersed PS particles via soap-free emulsion polymerization, in which the cross-linking agent (DVB) was delayed addition by varying time (Delayed Addition Method, DAM). Through this method, the highly cross-linked monodispersed particles with functional groups on its surface can be prepared. The particles prepared by DAM had a uniform size distribution for the St/DVB and St/HEMA/DVB system. For the St/DVB system, when the cross-linking agent (DVB) was added delay 3 or 7 h, cross-linked PS particles could be successfully prepared without a significant change in the narrow particle size distribution even containing up to 40 wt% of DVB. Similarly, for the St/HEMA/DVB system, by delayed addition of DVB for 3 h, stable and monodispersed polymer particles still could be prepared even the containing of DVB reach to 60 wt%. Moreover, when the feed composition of the DVB kept constant, the longer the delayed addition time of DVB, the better the monodispersity of the cross-linked particles were.     

Effects of molar substitution of AA pendant on poly(MMA-co-GMA) under UV curing

The molar substitution of an acrylic acid (AA) pendant group on a glycidyl methacrylate–methyl methacrylate copolymer was investigated to evaluate its affects on mechanical properties and thermal stability under UV curing. Structural analysis was conducted by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy (¹H-NMR) to study the synthetic route of the acrylate copolymer. The mechanical behaviors of AA substituted copolymers were interpreted in terms of both their loss tangent and elongation at the break point, because AA increases the cross-linking density, which is directly proportional to the degree of homopolymerization; this relationship was monitored by ¹H-NMR with various molar substitutions. In addition, the optical and mechanical properties of the copolymers were also characterized by the extent of AA molar substitution. The optimal behavior was obtained at a molar substitution of 94.3% (equivalent to an AA/GMA molar ratio of 1.4) and satisfied both the transparency (>89.3%) and elongation (>7.4%) requirements for the complex-shaped coatings.