丙烯酰胺-甲基丙烯酸共聚物的NMR研究

用FT-IR光谱,1H-NMR谱,质子弛豫时间等方法研究了在热引发条件下甲基丙烯酸和丙烯酰胺的共聚合反应,讨论了甲基丙烯酸(MAA)、丙烯酰胺(AM)在不同配比,不同反应时间下的共聚合转化率,以及单体配比与聚合物链运动的关系。结果表明,随着甲基丙烯酸(MAA)含量增大,共聚合转化率呈先增大后减小趋势。当AM与MAA物质的量之比为2∶1,热引发共聚合反应时间为3 h,共聚合转化率可达90.2%。从自旋-晶格弛豫时间(T1)和自旋-自旋弛豫时间(T2)的测定得出,当单体配比中MAA含量增加,大分子运动的相关时间(τ)变长,大分子中质子的平均间距变小,链段运动变慢,而高频短程运动则变化不明显。     

PMMA-b-PBMA-b-PNVIm(Bu)BF_4离子液体嵌段聚合物的RAFT合成及表征

以S-十二烷基-S′-(α,α′-二甲基-α″-乙酸)-三硫代碳酸酯为链转移剂,制备了窄分布的聚甲基丙烯酸甲酯(PMMA)大分子链转移剂,用大分子链转移剂来引发第二单体甲基丙烯酸丁酯(BMA)制备了PMMA-b-PBMA二嵌段聚合物。再以二嵌段聚合物为大分子链转移剂引发N-乙烯基咪唑(NVIm)合成PMMA-b-PBMA-b-PNVIm三嵌段聚合物。通过与溴代正丁烷发生季铵化反应并与氟硼酸钠进行阴离子交换得到离子液体嵌段聚合物PMMA-b-PNVIm(Bu)BF_4。运用核磁、红外和凝胶渗透色谱及差示扫描量热等技术对产物的结构、分子量及分子量分布和玻璃化转变温度进行表征。结果表明,嵌段聚合物为PMMA166-b-PBMA145-b-PNVIm144,分子量分布为1.68,合成过程具有活性/可控聚合特征。     

聚苯胺功能化多壁碳纳米管/环氧树脂复合材料的热性能与电性能研究

采用可溶性导电聚苯胺功能化多壁碳纳米管(PANI-MWNTs)与环氧树脂(Epoxy)溶液共混制备了PANIMWNTs/Epoxy复合材料。当PANI-MWNTs溶解分散于Epoxy溶液中时,包覆在MWNTs表面的PANI分子链溶解和溶胀把MWNTs隔开,使MWNTs均匀分散在Epoxy中。MWNTs良好地分散及MWNTs与Epoxy间的界面粘结作用,阻碍Epoxy大分子链段的运动和热分解在复合材料中的传播,复合材料的玻璃化转变温度和热稳定性显著提高。PANI-MWNTs的引入使复合材料电导率上升,当其含量为1.25wt%时,复合材料的室温电导率为9.35×10-6 S·cm-1比Epoxy提高7个数量级。     

聚砜及其共混物T_(11)转变的TBA研究

在非晶态高聚物玻璃化转变温度以上是否存在整个大分子链运动的转变,即液-液转变(T_(11)),目前仍有争议。本文借助扭辮分析法(TBA)的研究结果明显地表明:双酚A型聚砜和聚碳酸酯存在T_(11)转变(>T_g),并且着重地考察了热历史、反应性增塑剂以及高聚物的共混对聚砜的T_(11)转变过程的影响。     

聚丙烯玻璃化转变温度的分子动力学模拟

对等规、间规、无规三种不同聚丙烯(PP)的玻璃化转变温度进行了分子动力学模拟。用分子动力学模拟来获得不同构型聚丙烯在不同温度下的特征体积,通过对模拟得到的体积-温度(V-T)作图,求得玻璃化转变温度,其模拟结果与实验值吻合得较好。同时分析了聚丙烯主链柔顺性、立构规整度和力场能量项对PP玻璃化转变温度的影响,模拟结果表明,二面角扭转能和非键能在玻璃化转变温度附近出现拐点,这是高分子出现玻璃化转变的主要根源。     

尼龙66/聚酚氧树脂共混体系的相容性EI北大核心CSCD

针对尼龙66与聚酚氧树脂共混体系的相容性展开研究。将尼龙66与聚酚氧树脂以不同配比进行熔融共混,使用动态力学分析仪测定共混样品中两个组分的玻璃化转变温度,使用差示扫描量热仪测定共混样品中尼龙66组分的熔点和结晶度,并且根据Nishi-Wang方程计算共混体系中尼龙66与聚酚氧之间的相互作用参数,以此分析尼龙66与聚酚氧树脂之间的共混相容性。研究发现,聚酚氧分子链中的羟基与尼龙66分子链中的酰胺基团之间的氢键作用使尼龙66与聚酚氧部分相容;聚酚氧在尼龙66相中的部分溶解造成PA66组分的玻璃化转变温度上升;由于尼龙66与聚酚氧之间的氢键对聚酚氧链段运动的束缚作用强于尼龙66的链柔性对聚酚氧链段运动的促进作用,尼龙66在聚酚氧相中的部分溶解导致聚酚氧组分的玻璃化转变温度不降反升。随着聚酚氧含量增加,共混物中尼龙66的结晶熔点和结晶度均随之下降;共混体系中尼龙66与聚酚氧的相互作用参数为负值,但共混体系呈现"海-岛"两相结构。     

尼龙66/聚酚氧树脂共混体系的相容性

针对尼龙66与聚酚氧树脂共混体系的相容性展开研究。将尼龙66与聚酚氧树脂以不同配比进行熔融共混,使用动态力学分析仪测定共混样品中两个组分的玻璃化转变温度,使用差示扫描量热仪测定共混样品中尼龙66组分的熔点和结晶度,并且根据Nishi-Wang方程计算共混体系中尼龙66与聚酚氧之间的相互作用参数,以此分析尼龙66与聚酚氧树脂之间的共混相容性。研究发现,聚酚氧分子链中的羟基与尼龙66分子链中的酰胺基团之间的氢键作用使尼龙66与聚酚氧部分相容;聚酚氧在尼龙66相中的部分溶解造成PA66组分的玻璃化转变温度上升;由于尼龙66与聚酚氧之间的氢键对聚酚氧链段运动的束缚作用强于尼龙66的链柔性对聚酚氧链段运动的促进作用,尼龙66在聚酚氧相中的部分溶解导致聚酚氧组分的玻璃化转变温度不降反升。随着聚酚氧含量增加,共混物中尼龙66的结晶熔点和结晶度均随之下降;共混体系中尼龙66与聚酚氧的相互作用参数为负值,但共混体系呈现"海-岛"两相结构。     

溶聚丁苯橡胶玻璃化转变温度的主要影响因素研究

采用活性阴离子聚合方法和分子结构设计技术制备出具有不同分子结构参数的溶聚丁苯橡胶(SSBR)。研究了SSBR的结合苯乙烯含量、1,2-聚丁二烯含量、分子量、分子量分布(聚合物分散性指数PDI)以及嵌段结构等对SSBR生胶玻璃化转变温度的影响。结果表明,结合苯乙烯含量、1,2-聚丁二烯含量和嵌段结构是溶聚丁苯橡胶玻璃化转变温度的主要影响因素,对阻尼性能有着显著影响。     

丙烯酸酯改性胺固化剂对环氧树脂防火涂料玻璃化转变温度及性能的调控EI北大核心CSCD

文中利用Michael加成反应得到了不同碳链长度的丙烯酸酯改性三乙烯四胺固化剂,并将其用于制备环氧树脂基膨胀防火涂料。采用核磁共振氢谱对所得改性固化剂进行了表征;差示扫描量热分析证明,将不同碳链长度的丙烯酸酯结构引入固化剂分子中可以有效对环氧树脂交联体系的玻璃化转变温度进行调节(玻璃化转变温度在41.4~101.5℃之间变化);采用热失重分析和极限耐火测试对防火涂料的防火效果进行了测试;采用扫描电镜对耐火测试后炭层的微观形貌进行了分析。结果表明,涂料的防火性能与固化剂的种类即固化体系的玻璃化转变温度密切相关,当采用丙烯酸十二烷基酯改性三乙烯四胺为固化剂时,固化环氧树脂的玻璃化转变温度为87.6℃,其防火涂料的极限耐火时间最长,达到43.2min,膨胀倍率为12,拥有致密、连续的炭层结构,其平均孔径为1.75μm。同时,丙烯酸酯改性三乙烯四胺制备的环氧漆膜的耐紫外老化性能和韧性都得到了提高。     

二苯醚异氰酸酯聚醚氨酯的合成及性质EI

合成了以聚四氢呋喃(PTMO)为软段,4,4’-二异氰酸二苯醚(ODI)和不同扩链剂[乙二胺(EDA、丁二醇(BD)、N,N-二羟乙基甲胺(MDEA)]为硬段的链段型聚氨酯。并通过MDEA的第三胺和γ-丙磺酸内酯反应,转化为双离子型离聚体。用差示扫描量热、动态力学性能、应力-应变以及紫外老化等实验方法研究了化学组成和氨磺化程度对材料相分离程度、力学性能和形态结构的影响。     

Synthesis and characterization of polydioxolane polyurethane ionomer

A series of novel sodium salts of sulfonated polyurethane ionomers with polydioxolane as soft segment was successfully synthesized and their properties were characterized by means of Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and complex impedance analysis. As the ionization level increased, the compatibility of the hard segments and soft segments was improved and the glass transition region of soft segment became broader. The effects of ionization level, temperature, chemical components of soft segment on ionic conductivity of ionomers were investigated in detail. Adjusting the ionization level and incorporating PEG soft segment into the PDXL-PU ionomers, a new type of solid polymer electrolyte material with good mechanical properties and high ionic conductivity could be obtained.     

Influence of nanoparticles on glass transition of polymers

Tunability of glass transition temperature of poly-methylmethacrylate has been achieved using homogeneously dispersed gold nanoparticles of different weight fraction within the polymer matrix. Remarkably, depression in glass transition temperature with respect to the neat polymer was observed for poly-methylmethacrylate (120 K and 15 K) by varying the weight fraction of the gold nanoparticles contrary to the conventional results in literature which shows elevation in Tg for attractive polymer-particle interaction, as is the case here. The magnitude of the shift in glass transition temperature is large for the higher of the two molecular weight of poly-methylmethacrylate studied here. Possible explanations of the observed behavior are provided, although more experiments are underway to unravel the intricacies of the observed phenomena.     

Local polymer dynamics in polymer-C60 mixtures

The complexity of intermolecular interactions in polymer-nanoparticle systems leads to spatial variations in structure and dynamics at both the meso- and nanoscale. Much of this behavior is manifested in properties such as the glass transition and the viscosity. Incoherent neutron scattering measurements of C60-polymer mixtures reveal that local polymer chain backbone motions in the glassy state are suppressed relative to those of the pure polymer. Moreover, the scattering spectrum of the melt suggests that the influence of C60 on polymer dynamics is limited to the vicinity of the particles at nanosecond time scales. A model is presented to reconcile these observations with the bulk dynamical properties exhibited by the mixtures.     

非晶态高分子粉体玻璃化转变温度的影响因素及测试技术

非晶态高分子粉体的玻璃化转变温度，是分析其结块原因、采取预防结块措施的重要依据。本文分析了影响非晶态高分子粉体玻璃化转变温度的主要因素；介绍了常用玻璃化温度测试技术；建立了用膨胀法测试非晶态粉体玻璃化转变温度的装置与方法，并讨论了其有效性与准确性。     

A thermally tunable inverse opal photonic crystal for monitoring glass transition

An optical method was developed to monitor the glass transition of the polymer by taking advantage of reflection spectrum change of the thermally tunable inverse opal photonic crystal. The thermally tunable photonic bands of the polymer inverse opal photonic crystal were traceable to the segmental motion of macromolecules, and the segmental motion was temperature dependent. By observing the reflection spectrum change of the polystyrene inverse opal photonic crystal during thermal treatment, the glass transition temperature of polystyrene was gotten. Both changes of the position and intensity of the reflection peak were observed during the glass transition process of the polystyrene inverse opal photonic crystal. The optical change of inverse opal photonic crystal was so large that the glass transition temperature could even be estimated by naked eyes. The glass transition temperature derived from this method was consistent with the values measured by differential scanning calorimeter.     

Influence of vitrification on defect formation during curing of epoxies

Defect formation in epoxies due to the chemical shrinkage was observed during isothermal cure over a wide cure temperature range. The observed defects were cohesive cracks and adhesional failures. The influence of the mutual position of the gel and the glass transition points on shrinkage-defect formation was examined. The different types of the cohesive defects can arise in the curing system in both the rubbery and glassy state. The type of defect formed was found to be determined by the relaxational state of the polymer during defect formation. The dependence of the glass transition temperature upon the degree of polymerization is reported for the epoxy/amine polymer system investigated. Experimental parameters of polymer resistance to chemical shrinkage cracking were measured for all investigated cure temperatures.     

Dielectric relaxation of relaxor ferroelectric P(VDF-TrFE-CFE) terpolymer over broad frequency range

Dielectric properties of a relaxor ferroelectric polymer, poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) [P(VDF-TrFE-CFE)] terpolymer, were investigated over a broad range of frequency (from 0.1 kHz to 1 GHz) and a broad range of temperature (-20degC to 76degC). Time-temperature superposition was used to extrapolate the dielectric constant to high frequencies (~1 GHz) from low frequency data (<1 MHz). The consistency between the directly measured and the extrapolated data indicate that the time-temperature superposition can be applied at temperature ranging from the glass transition to the broad ferroelectric-paraelectric transition peak of relaxor, indicating that the glass transition is still the dominating relaxation process at room temperature for the ferroelectric relaxor. Compared with the dielectric properties of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer, the terpolymer shows a higher dielectric constant even at 1 GHz, which is considered to originate from the random defects modification converting the long-chain polar-molecular conformation to short-range molecular microstructures and enhancing the molecular motions in both polar and nonpolar nanodomains.     

A Critical Assessment of Experimental Methods for Determining the Dynamic Mechanical Characteristics of Shape Memory Polymers

Experimental study of temperature‐ and frequency‐dependent properties of the commercially available shape memory polymer Tecoflex? EG 72D (TFX) (Lubrizol, USA) using dynamic mechanical analysis (DMA) technique is presented. Temperature scan DMA tests have been carried out in three distinct deformation modes, uniaxial tension, three‐point bending, and simple torsion, using two different testing rigs at different test parameters (frequency, strain amplitude, and heating rate) in temperatures ranging from below to above the glass transition temperature. The influence of different test parameters and some discrepancies in the temperature‐dependent storage and loss moduli (and hence the loss factor) measured by DMA in different deformation modes are discussed.     

氧亚甲基连接的聚氧化乙烯统计共聚物的热性能研究EI

研究了统计共聚物(Statistic Copolymer)氧亚甲基连接的聚氧化乙烯(OM-POE)的热力学行为,探索了聚合物链中氧化乙烯链段的平均长度和长度分布对聚合物及其共混物的玻璃化温度、熔点、熔化热及结晶度的影响。结果表明,不同长度的氧化乙烯链段无规地进入分子链中,熔点与组成的关系可用Flory的无规共聚物熔点方程来描述。     

Application of sample-sample two-dimensional correlation spectroscopy to determine the glass transition temperature of poly(ethylene terephthalate) thin films

The glass transition temperatures (Tg) of poly(ethylene terephthalate) (PET) thin films with different thicknesses are determined by analyzing their in situ reflection-absorption infrared (RAIR) spectra measured over a temperature range of 28 to 84 degrees C. The criterion of standard deviation of the covariance matrices is used as a graphical indicator for the determination of the Tg present in the sample-sample two-dimensional (2D) correlation spectra calculated from the temperature-dependent RAIR spectra. After two data pretreatments of the first derivative of the spectral absorbance versus temperature and the mean normalization over the wavenumbers are sequentially carried out on the RAIR spectra, an abrupt change of the first-derivative correlation spectra with respect to temperature is quickly obtained. It reflects the temperature at which the apparent intensity changes in pertinent absorption bands of PET thin films take place due to the dramatic segmental motion of PET chain conformation. The Tg of the thin PET films is accordingly determined. The results reveal that it decreases with a great dependence on the film thickness and that sample-sample 2D correlation spectroscopy enables one to determine the transition temperature of polymer thin films in an easy and valid way.