Ultrasound-assisted dyeing of cellulose acetate

The possibility of reducing the use of auxiliaries in conventional cellulose acetate dyeing with Disperse Red 50 using ultrasound technique was studied as an alternative to the standard procedure. Dyeing of cellulose acetate yarn was carried out by using either mechanical agitation alone, with and without auxiliaries, or coupling mechanical and ultrasound agitation in the bath where the temperature range was maintained between 60 and 80 °C.The best results of dyeing kinetics were obtained with ultrasound coupled with mechanical agitation without auxiliaries (90% of bath exhaustion value at 80 °C). Hence the corresponding half dyeing times, absorption rate constants according to Cegarra–Puente modified equation and ultrasound efficiency were calculated confirming the synergic effect of sonication on the dyeing kinetics. Moreover the apparent activation energies were also evaluated and the positive effect of ultrasound added to mechanical agitation was evidenced by the lower value (48 kJ/mol) in comparison with 112 and 169 kJ/mol for mechanical stirring alone with auxiliaries and without, respectively.Finally, the fastness tests gave good values for samples dyed with ultrasound technique even without auxiliaries. Moreover color measurements on dyed yarns showed that the color yield obtained by ultrasound-assisted dyeing at 80 °C of cellulose acetate without using additional chemicals into the dye bath reached the same value yielded by mechanical agitation, but with remarkably shorter time.     

Poly(2‐vinyl pyridine)‐block‐Poly(ethylene oxide) Featuring a Furan Group at the Block Junction—Synthesis and Functionalization

Furfuryl glycidyl ether (FGE) represents a highly versatile monomer for the preparation of reversibly cross‐linkable nanostructured materials via Diels–Alder reactions. Here, the use of FGE for the mid‐chain functionalization of a P2VP‐b‐PEO diblock copolymer is reported. The material features one furan moiety at the block junction, P2VP₆₈‐FGE‐b‐PEO₃₉₀, which can be subsequently addressed in Diels–Alder reactions using maleimide‐functionalized counterparts. The presence of the FGE moiety enables the introduction of dyes as model labels or the formation of hetero‐grafted brushes as shell on hybrid Au@Polymer nanoparticles. This renders P2VP₆₈‐FGE‐b‐PEO₃₉₀, a powerful tool for selective functionalization reactions, including the modification of surfaces.

     

Electrocyclic [1,5] hydrogen shift in the thermal elimination kinetics of phenyl acetate and p-tolyl acetate in the gas phase: a density functional theory study

The kinetics and mechanisms of thermal decomposition of phenyl acetate and p-tolyl acetate in the gas phase were studied by means of electronic structure calculations using density functional theory methods: B3LYP/6-31G(d,p), B3LYP/6-31++G(d,p), B3PW91/6-31G(d,p), B3PW91/6-31++G(d,p), MPW1PW91/6-31G(d,p), MPW1PW91/6-31++G(d,p), PBE/6-31G(d,p) and PBE/6-31++G(d,p). Two possible mechanisms have been considered: mechanism A is a stepwise process involving electrocyclic [1,5] hydrogen shift to eliminate ketene through concerted six-membered cyclic transition-state structure, followed by tautomerisation of cyclohexadienone or by 4-methyl cyclohexadienone intermediate to give the corresponding phenol. Mechanism B is a one-step concerted [1,3] hydrogen shift through a four-membered cyclic transition-state geometry, to produce ketene and phenol or p-cresol. Theoretical calculations showed reasonable agreement with experimental activation parameters when using the Perdew, Burke and Ernserhof (PBE)functional, through the stepwise [1,5] hydrogen-shift mechanism. For mechanism B, large deviation for the entropy of activation was observed. No experimental data were available for p-tolyl acetate; however, theoretical calculations showed similar results to phenyl acetate, thus supporting the stepwise mechanism for both phenyl acetate and p-tolyl acetate.     

Effect of UV radiation on the optical and some structural properties of irregular rayon acetate fibers

This recent study shed demonstration on how the structural parameters changes due exposure to UV radiation and different wavelengths. So this article throws light on the changes of the optical properties and some structural properties due exposure to UV radiation and different wavelengths on irregular rayon acetate fibers. Pluta polarizing interference microscope is used to study the changes for refractive indices and birefringence with different exposure times at three different intensities on irregular rayon acetate fibers. As the principal optical parameters determined, these give an indication of the isotropic refractive index, stress optical coefficient, stress due to UV radiation, optical configuration parameter, segment anisotropy, the number of molecules per unit volume and polarizability of a monomer unit can be obtained. Also by using different wavelengths are given the spectral dispersions, Cauchy's dispersion constants, the resonant wavelength, the oscillation energy, the dispersion energy, the dielectric constant and the dielectric susceptibility for rayon acetate fibers with different wavelengths at room temperatures. Illustrations are given using graphs and microinterferograms.     

聚（1-乙烯基-3-乙酸烷基酯咪唑）阳离子／P（MMA．VAc）聚合物电解质

合成了一系列由聚（1-乙烯基-3-乙酸烷基酯咪唑）阳离子和二（三氟甲基磺酰亚胺）阴离子（TFSI）组成的聚离子液体并进行了表征．热重分析（TGA）和电导率分析表明,在聚（甲基丙烯酸甲酯,醋酸乙烯酯）（P（MMA—VAc））基体中掺杂聚离子液体后,体系的热稳定性和离子电导率均大为改善,红外光谱（FT—IR）、示差扫描量热分析（DSC）、X射线衍射（XRD）和扫描电子显微镜（SEM）等测试结果亦可佐证．讨论了离子液体的结构以及不同种锂盐（LiC104,LiBF4,LiTFSI）对电解质性能的影响．由PIL／P（MMA—VAc）／LiTFSI组成的共混电解质膜,在可见光下透过率≥90％,可作为离子导电材料用于电致变色器件（ECD）,显示了其优良的电化学性能．     

Synthesis and characterization of in-chain silyl-hydride functional SBR and self-crosslinking elastomer

Functional in-chain silyl-hydride(Si-H) SBR copolymers of 4-vinyiphenyldimethylsilanol(VPDMS) and butadiene were synthesized by living anionic polymerization,in which active group Si-H was not lost and its content was controllable. Corresponding self-crosslinking elastomers were obtained by hydrosilation of Si-H group with vinyl bonds in chain.The copolymers and elastomers were characterized by ~1H NMR,size exclusion chromatography(SEC),Fourier transform infrared (FTIR) spectroscopy,differential scanning calorimetry(DSC),and thermogravimetry analysis(TGA) techniques.     

一种含假芪型偶氮生色团两亲性嵌段共聚物的合成与表征

利用原子转移自由基聚合（ATRP）合成了一种新型的含假芪型偶氮生色团的两亲性嵌段共聚物P（HEMA-b-6CNAzo）。首先,采用ATRP引发剂引发三甲基硅保护的羟乙基甲基丙烯酸酯（HEMA—TMS）聚合,得到大分子引发剂P（HEMA—TMS）;接着进一步引发单体甲基丙烯酸6-（N_甲基苯胺基）己酯进行ATRP反应,得...     

碳酸二甲酯和乙酸苯酯合成碳酸二苯酯MoO3催化剂的失活研究

利用直接焙烧法在400℃焙烧(NH4)6MoO7O24.4H2O制备了碳酸二甲酯(DMC)与乙酸苯酯(PA)酯交换合成碳酸二苯酯(DPC)反应的正交晶系MoO3催化剂,通过比表面积(BET)、X射线衍射(XRD)、X射线光电子能谱(XPS)、傅立叶变换红外光谱(FT-IR)、扫描电镜(SEM)等技术,对MoO3催化剂在失活前后的结构和形貌进行了分析,探讨了MoO3催化剂的失活行为.结果表明,正交晶系MoO3的(021)、(110)晶面有利于酯交换反应,多次使用后,催化剂表面有无定形碳的物理沉积,催化剂比表面积降低,催化剂颗粒长径比发生了改变,催化剂(021)、(110)晶面衍射峰强度减弱,进而导致了MoO3催化剂的失活.