Interchange reaction kinetics and sequence distribution of liquid crystalline poly(ethylene terephthalate-co-2(3)-chloro-1,4-phenylene terephthalate)

Liquid crystalline (LC) poly(ethylene terephthalate-co-2(3)-chloro-1,4-phenylene terephthalate) [copoly(ET/CPT)] was prepared using poly(ethylene terephthalate) (PET) as a flexible spacer, terephthalic acid (TPA), and chlorohydroquinone diacetate (CHQDA). All reactions involved in the copolymerization were investigated using some model compounds: TPA was used for acidolysis, diphenylethyl terephthalate (DPET) for interchange reaction between PET chains, and di-o-chlorophenyl terephthalate (DOCT) and di-m-chlorophenyl terephthalate (DMCT) for interchange reaction between PET and rigid rodlike segments. Activation energies obtained for the acidolysis of PET with TPA and for interchange reaction of PET with DPET, DOCT, and DMCT were 19.8 kcal/mole, 26.5 kcal/mole, 60.2 kcal/mole, and 45.9 kcal/mole, respectively. This result supports that the copolymerization proceeds through the acidolysis of PET with TPA first and subsequent polycondensation between carboxyl end group and CHQDA or acetyl end group, which is formed from the reaction of CHQDA and TPA. Also, it was found that ester-interchange reaction can be influenced by the steric hindrance. Copoly(ET/CPT)s obtained had ethylene acetate end groups formed from acetic acid and hydroxy ethylene end groups and showed almost the random sequence distribution for all compositions.     

Thermal properties of Poly(trimethylene terephthalate)/Poly(ethylene terephthalate) melt blends

The thermal behavior, morphology, ester-interchange reaction of Poly(trimethylene terephthalate) (PTT)/Poly(ethylene terephthalate) (PET) melt blends were investigated over the whole composition range(xPTT/(1-x)PET) using a twinscrew Brabender. The melt blends were analyzed by differential scanning calorimetry (DSC), nuclear magnetic resonance spectroscopy (¹³C-NMR), and scanning electron microscopy (SEM). Single glass transition temperature (T _g ) and cold crystallization temperature (T _cc ) were observed in all melt blends. Melt blends were found to be due to the ester-interchange reaction in PTT/PET blend. Also the randomness of copolymer increases because transesterification between PTT and PET increases with increasing blending time. This reaction increases homogeneity of the blends and decreases the degree of crystallinity of the melt blends. In PTT-rich blends, mechanical properties decrease with increase of PET content compared with that of pure PTT. And, in PET-rich blends, tensile modulus decreases with increase of PTT content, but tensile strength and elongation is similar to that of pure PET.     

Miscibility and crystallization behaviors of poly(trimethylene terephthalate)/poly(ethylene naphthalate) blends

Poly(trimethylene terephthalate) (PTT)/poly(ethylene naphthalate) (PEN) blends of various compositions were prepared by the solution-blending and melt-blending methods. The changes in miscibility and crystallization behaviors of the blends upon thermal treatment above the melting temperature of the blends at 280°C were investigated by using DSC, DMA,¹H NMR, and SAXS analyses. Without any thermal treatment, the blend systems were not miscible, and the thermal transitions, such as glass transition, cold crystallization, and crystal melting of the individual components were observed in the DSC and DMA analyses. With thermal treatment, though, they became miscible as the thermal transitions of each component disappeared and single glass transition peaks were observed in the thermal analysis. The chain randomness determined using¹H NMR spectroscopy revealed that thermal treatment at 280°C for more than 30 min brought about transesterification reactions between the PTT and PEN segments resulting in an increase in their miscibility. These results were confirmed by the small angle X-ray analysis conducted to determine the long period (L), the thickness of the crystalline lamella stack (l _c ), and the thickness of the amorphous region (l _a ). After short thermal treatment, the melt-blended sample followed the values for the individual components. However, with extended thermal treatment, the blend became homogeneous, possessing different crystalline morphologies which resulted in different values ofL, l _c , andl _a .     

The preparation and characterization of conductive poly(ethylene terephthalate)/polyaniline composite fibers using benzoyl peroxide

Conductive polyaniline (PAn)/poly(ethylene terephthalate) (PET) composite fibers were prepared by chemical polymerization of aniline in the presence of PET fibers using benzoyl peroxide (Bz₂O₂) in organic solvent/aqueous hydrochloric acid mixtures. The effects of polymerization conditions such as organic solvent/water ratio, oxidant, aniline and hydrochloric acid concentrations and temperature were investigated on the amount of PAn deposited on PET fiber and the electrical surface resistance of composite fibers. The maximum PAn content and the lowest electrical surface resistance of composite fibers were observed at HCl concentrations of 0.5 mol L⁻¹. The properties of PAn/PET composite fibers such as density, diameter, tensile strength and breaking elongation were also investigated in comparison with those of pure PET. Characterization of conductive composite fibers was carried out by FTIR, TGA, SEM techniques, surface resistance measurements, and cross section images taken by optical microscope.     

Miscibility of flame retardant epoxy resin with poly(ethylene terephthalate) and the characterizations of the blends

Epoxy resin containing bromine compound was melt blended with PET to obtain flame retardant polymer. The blend product was characterized by DSC, SEM, intrinsic viscosity and melt index measurements. The reaction between the epoxy group of DGEBBA (diglycidyl ether of brominated bisphenol A) and the carboxyl (or hydroxyl) end group of PET led to cross-linking of PET chains, and the intrinsic viscosity and melt index (MI) were increased in the range of equivalent amount of epoxy resin (within 1 %). DSC data revealed that the epoxy resin was not located in the crystalline region but was appeared in the amorphous region of PET matrix. Good miscibility of epoxy resin resulted in the decrease of crystallization temperature and glass transition temperature of PET. The blend was spun into fiber without any problems such as swelling or draw resonance, however, the mechanical properties were decreased as the amount of the DGEBBA was increased.     

Thermal and mechanical properties of modified CaCO3 filled poly (ethylene terephthalate) nanocomposites

Poly(ethylene terephthalate) (PET)/CaCO₃ and PET/modified-CaCO₃ (m-CaCO₃) nanocomposites were prepared by melt blending. The morphology indicated that m-CaCO₃ produced by reacting sodium oxalate and calcium chloride, was well dispersed in PET matrix and showed good interfacial interaction with PET compared to CaCO₃. No significant differences in the thermal properties such as, glass transition, melting and degradation temperatures, of the nanocomposites were observed. The thermal shrinkage of PET at 120 °C was 10.8 %, while those of PET/CaCO₃ and PET/m-CaCO₃ nanocomposites were 2.9–5.2 % and 1.2–2.8 %, respectively depending on filler content. The tensile strength of PET/CaCO₃ nanocomposite decreased with CaCO₃ loading, whereas that of PET/m-CaCO₃ nanocomposites at 0.5 wt% loading showed a 17 % improvement as compared to neat PET. The storage modulus at 120 °C increased from 1660 MPa for PET to 2350 MPa for PET/CaCO₃ nanocomposite at 3 wt% loading, and 3230 MPa for PET/m-CaCO₃ nanocomposite at 1 wt% loading.     

The effect of molecular weight and the linear velocity of drum surface on the properties of electrospun poly(ethylene terephthalate) nonwovens

In this study, we evaluated the effect of the molecular weight of the polymer on electrospun poly(ethylene terephthalate) (PET) nonwovens, and their mechanical properties as a function of the linear velocity of drum surface. Polymer solutions and electrospun PET nonwovens were characterized by means of viscometer, tensiometer, scanning electron microscope (SEM), wide angle X-ray diffraction measurement (WAXD) and universal testing machine (UTM). By keeping the uniform solution viscosity, regardless of molecular weight differences, electrospun PET nonwovens with similar average diameter could be obtained. In addition, the mechanical properties of the electrospun PET nonwovens were strongly dependent on the linear velocity of drum surface. From the results of the WAXD scan, it was found that the polymer took on a particular molecular orientation when the linear velocity of drum surface was increased. The peaks became more definite and apparent, evolving from an amorphous pattern at 0 m/min to peaks and signifying the presence of crystallinity at 45 m/min.     

Crystallization and molecular relaxation of poly(ethylene terephthalate) annealed in supercritical carbon dioxide

Poly(ethylene terephthalate) was annealed at different temperature and pressure of supercritical carbon dioxide (CO₂) using samples quenched from the melt. Crystallization and molecular relaxation behavior due to CO₂-annealing of samples were investigated using differential scanning calorimetric and dynamic mechanical measurements. The glass transition and crystallization temperatures significantly decreased with increasing temperature and pressure of CO₂. The dynamic mechanical measurement of samples annealed at 150 °C in supercritical CO₂ showed three relaxation peaks, corresponding to existence of different amorphous regimes such as rigid, intermediate, and mobile domains. As a result, the mobile chains were likely to facilitate crystallization in supercritical state. It also led to the decreased modulus of CO₂-annealed samples with increasing pressure.     

Synthesis and hydrophilicity of poly(trimethylene 2,6-naphthalate)/poly(ethylene glycol) copolymers

Poly(trimethylene 2,6-naphthalate) (PTN)/poly(ethylene glycol) (PEG) copolymers were synthesized by the two-step melt copolymerization process of dimethyl-2,6-naphthalenedicarboxylate (2,6-NDC) with 1,3-propanediol (PD) and PEG. The copolymers produced had different PEG molecular weights and contents. The structure, thermal property, and hydrophilicity of these copolymers were studied by proton nuclear magnetic resonance (¹H-NMR) analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and by contact angle, moisture content, and instantaneous elastic recovery measurements. The intrinsic viscosity and the instantaneous elastic recovery of the PTN/PEG copolymers increased with increasing PEG molecular weight and content, whereas the glass transition, melting, and cold crystallization temperatures, and the heat of fusion of the PTN/PEG copolymers all decreased with increasing PEG molecular weight or content. The thermal stability of the copolymers was not affected by PEG molecular weight or content. The hydrophilicity, as determined by contact angle and moisture content measurements of the copolymer films, was significantly improved with increasing PEG molecular weight and content.     

The effect of casting solvent on the structural characteristics and miscibility of regenerated silk fibroin/Poly(vinyl alcohol) blends

Regenerated silk fibroin(SF)/Poly(vinyl alcohol)[PVA] blend films were prepared using different casting solvents, water and formic acid, to elucidate the effect of casting solvent on the structure and miscibility of SF/PVA blends. FTIR and XRD measurement suggested thatβ-sheet conformation of SF was not changed by addition of PVA in case of formic acid casting and the casting solvent determined the crystallized component of SF/PVA, leading to a different trend in the overall crystallinity between the two blends. The casting solvent had a dominant role in deciding phase behavior and molecular miscibility of blend films. SEM observation and DMTA measurement elucidated that water solvent produced phase-separated blend films while formic acid yielded one phase blend films with partial miscibility in molecular level indicating that the miscibility of SF blend can be improved by choosing a proper co-solvent.     

Effects of Cultivar and Environment on β-(1,3)-(1,4)- -glucan Content and Acid Extract Viscosity of Spanish Barleys

The acid extract viscosities and β-glucan contents of ten two- and six-rowed barley cultivars grown at seven locations in three consecutive years in Spain were studied in the present work. The viscosities varied from 2·4 to 24·8 centistokes (cSt) and the mean value was 6·4 cSt. The average β-glucan content of barleys determined by HPLC was 3·5% with a range of 1·9–5·5%. Significant differences were found in both β-glucan content and acid extract viscosity between different cultivars, locations and years. The β-glucan contents and viscosities of winter cultivars were higher than those of spring. Cvs. Barbarrosa and Hatif de Grignon were the genotypes with the highest values for both parameters, while cv. Beka had the lowest viscosity and β-glucan content. Environmental factors influenced both parameters. The acid extract viscosities of barleys were correlated negatively with the amount of precipitation (r=−0·754;P<0·05). Barleys grown in wet and rainy areas (Girona and La Coruña) had lower viscosity values.     

蓖麻三磷酸甘油脱氢酶基因 (RcGPDH)的克隆及功能分析

为了阐明蓖麻三磷酸甘油脱氢酶基因（glycerol-3-phosphate dehydrogenase, RcGPDH）在蓖麻油累积过程中的作用,本研究根据已报道的蓖麻种子表达序列标签（Expressed Sequence Tags,EST）设计引物,通过RACE（rapid-amplification of cDNA ends)方法克隆蓖麻RcGPDH基因的全长并对其序列进行分析,构建了该基因的酵母表达载体PYES2.1/V5-His-TOPO-RcGPDH,以载体PYES2.1/V5-His/lacZ质粒DNA为对照,转化酵母野生型菌株BY4742,运用分光光度法测定转基因酵母的生长曲线,通过香草醛法测定稳定生长期的转基因酵母的油脂含量。结果表明,转基因菌株比转空载体对照菌株生长慢,两者均在培养18h后进入平台期;两个菌株的油脂含量没有明显的差别,表明RcGPDH基因对酵母油脂的累积没有起到积极的作用,在蓖麻种子中可能还存在另一个GPDH同源基因参与TAG的合成。     

湖北稻茬小麦主茎、分蘖1、分蘖2和分蘖3的成穗率、产量贡献率及主要农艺性状分析

合理的茎蘖组合是提升小麦绿色高效生产的重要因素。为了解湖北稻茬小麦主要茎蘖对产量及主要农艺性状的影响,以大穗型小麦品种川麦104和多穗型小麦品种扬麦15为材料,于2016-2018年在湖北十堰和武汉两地稻茬麦大田条件下,设置低(1.35×106~1.65×106株·hm^-2)、中(2.85×106~3.15×106株·hm^-2)、高(4.35×106~4.65×106株·hm^-2)三种种植密度,分析了主茎(S)、分蘖1(T1)、分蘖2(T2)和分蘖3(T3)(按出现先后顺序)的成穗率、产量贡献率及相关农艺性状的表现。结果表明:(1)湖北稻茬小麦成穗茎蘖农艺性状表现值偏低,除穗长和茎高受品种的影响最大外,其他被测性状受影响程度表现为蘖位>种植密度>品种;(2)在主茎均能成穗的情况下,分蘖成穗率随蘖位和种植密度的升高而降低,大穗型品种川麦104的降幅大于多穗型品种扬麦15;(3)主茎产量贡献率随种植密度的升高而升高(35.12%~54.50%),分蘖1产量贡献率稳定在23.25%~25.50%,分蘖2和分蘖3的产量贡献率随种植密度升高而降低,分别为14.59%~23.22%和5.42%~16.77%;(4)主茎的穗粒数(35.94~44.13粒)和穗粒重(1.44~1.93 g)显著高于其分蘖,茎高、茎蘖收获指数和穗茎节长只在川麦104中、高种植密度下的分蘖3与其他茎蘖差异显著;穗长、可孕小穗数和不孕小穗数有随蘖位和种植密度升高而变劣的趋势。聚类分析得出:湖北稻茬小麦绿色高效生产模式,以主茎成穗为主体,低种植密度下增加分蘖1和分蘖2,争取分蘖3成穗为辅;中种植密度下争取分蘖1+分蘖2成穗为辅;而高种植密度下争取分蘖1成穗为辅。     

Evaluation of A1, A2, A3, A4(M), A4(G) and A4(VZM) cytoplasms in iso-nuclear backgrounds for grain mold resistance

Breeding for resistance to grain mold, an economically important disease of sorghum, has been only partially successful. Hybrid technology is well developed in sorghum due to availability of the cytoplasm male sterility (CMS) system and at present almost all commercial hybrids are based on the A₁ CMS system. To compare the available alternate CMS systems for grain mold resistance, 72 hybrids were produced by crossing 36 A-lines (six CMS systems; A₁, A₂, A₃, A_4(M), A_4(G), A_4(VZM) each in six nuclear backgrounds) with two common restorers, and were evaluated during the 2006 and 2007 rainy seasons in grain mold nursery at ICRISAT. Data analyses indicated influence of cytoplasm on the responses of hybrids to grain mold infection as measured by panicle grain mold resistance (PGMR) score. The A₁ cytoplasm seemed to contribute to grain mold resistance followed by A_4(VZM) and A₂ cytoplasms. The A_4(M) cytoplasm had superior general combining ability (GCA) effects while the A₁ and A_4(VZM) cytoplasm based hybrids had superior specific combining ability (SCA) effects on the PGMR score. Almost all hybrids had significant mid-parent heterosis. The A₁ cytoplasm is the best suited for the development of sorghum hybrids for the rainy season adaptation with grain mold resistance. However, use of alternate cytoplasms (A₂ and A_4(VZM)) for hybrid development will not increase susceptibility to grain mold in commercial grain production.     

盐胁迫下钾吸收途径的抑制对小麦叶片K~+、Na~+含量的影响

为研究盐胁迫下小麦维持钾、钠平衡的生理机制,以耐盐小麦沧麦6005和盐敏感小麦矮抗58为材料,利用TEA、NEM、Ba(NO_3)_2三种药物分别抑制钾离子通道、钾载体及非选择性阳离子通道,测定正常及盐胁迫下小麦叶片K~+、Na~+含量,比较耐盐性不同的小麦品种在K~+、Na~+吸收中的差异。结果显示,盐胁迫下,沧麦6005和矮抗58叶片K~+含量下降,Na~+含量增加;沧麦6005叶片Na~+含量低于矮抗58,K~+/Na~+比值高于矮抗58。正常条件下,NEM、TEA处理均可降低沧麦6005和矮抗58叶片K~+含量,NEM处理较TEA处理效果更为明显;TEA处理显著降低了盐胁迫下矮抗58叶片K~+含量,而NEM处理则明显降低了盐胁迫下沧麦6005的叶片K~+含量;TEA、NEM、Ba(NO_3)_2处理降低了盐胁迫下矮抗58叶片Na~+含量,仅NEM处理降低了沧麦6005叶片Na~+含量。综上所述,正常条件下,钾载体是小麦K~+吸收的主要方式;盐胁迫下,耐盐品种和盐敏感品种K~+吸收途径不同,耐盐品种的NSCCs和钾离子通道具有更强的"拒钠"能力。