Mechanical properties of Nylon-6/LDPE blends containing an epoxy resin compatibilizer

Binary and ternary blends of nylon-6/low density polyethylene (nylon-6/LDPE) and Nylon-6/LDPE/poly(ethylene-co-glycidyl methacrylate) were prepared by melt mixing. The blends exhibit two phase morphology with LDPE dispersed in the form of spherical domains in the nylon-6 matrix. The mechanical properties of the blends were measured by standard methods. It is shown that the use of the epoxy copolymer as a compatibilizer improves the impact strength of the blend as compared to nylon-6, which is attributed to better stress transfer across the interface due to the compatibilizer. The data for each mechanical property were also fitted into a best fit model equation and the method of steepest ascent was applied to arrive at the optimum composition of the blend for that property.

Effect of nanoparticle dispersion on glass transition in thin films of polymer nanocomposites

We present spectroscopic ellipsometry measurements on thin films of polymer nanocomposites consisting of gold nanoparticles embedded in poly(styrene). The temperature dependence of thickness variation is used to estimate the glass transition temperature, T(g). In these thin films we find a significant dependence of T(g) on the nature of dispersion of the embedded nanoparticles. Our work thus highlights the crucial role played by the particle polymer interface morphology in determining the glass transition in particular and thermo-mechanical properties of such nanocomposite films.

Enantio-differentiation of molecules with diverse functionalities using a single probe

This study reports (1S,2S)-N,N'-dihydroxy-N,N'-bis(diphenylacetyl)-1,2-cyclohexanediamine, a C-2 symmetric chiral hydroxamic acid ((S)-CBHA-DPA), as a unique probe for discrimination of molecules with diverse functionalities. The proposed CSA is also utilized for the accurate measurement of enantiomeric excess.

Estudo da influência do teor de segmentos hidrofílicos na síntese de poliuretanos dispersos em água

Considerações ambientais têm aumentado a pesquisa e o desenvolvimento de sistemas poliméricos aquosos para diversos tipos de aplicações, principalmente como revestimentos. Nesta dissertação, foram sintetizadas formulações não-poluentes à base de poliuretanos dispersos em água (PUDs), com 40% de teor de sólidos, na ausência de solventes orgânicos. Os monômeros empregados foram copolímeros em bloco à base de poli(glicol etilênico) e poli(glicol propilênico) (EG-b-PG), com teor de 25% de segmento hidrofílico EG, poli (glicol propilênico) (PPG), ácido dimetilolpropiônico (DMPA), diisocianato de isoforona (IPDI) e hidrazina (HYD), como extensor de cadeia. Foram variadas as razões entre o número de equivalente-grama de grupamentos isocianato e hidroxila (NCO/OH) e a proporção em equivalente-grama de PPG e dos copolímeros em bloco (EG-b-PG). Foi observado que a incorporação de altas quantidades de copolímero dificultou a síntese dos poliuretanos dispersos em água, levando à formação de géis. O tamanho médio de partícula e a viscosidade das dispersões foram determinados. Os filmes vazados a partir dessas dispersões foram avaliados quanto à capacidade de absorção de água, resistência mecânica, termogravimetria (TG), e caracterizados por espectroscopia na região do infravermelho (FTIR). As dispersões poliuretânicas produzidas se mostraram satisfatórias quando aplicadas como revestimento para madeira, metais e vidro

High performance non-volatile ferroelectric copolymer memory based on a ZnO nanowire transistor fabricated on a transparent substrate

A high performance ferroelectric non-volatile memory device based on a top-gate ZnO nanowire (NW) transistor fabricated on a glass substrate is demonstrated. The ZnO NW channel was spin-coated with a poly (vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) layer acting as a top-gate dielectric without buffer layer. Electrical conductance modulation and memory hysteresis are achieved by a gate electric field induced reversible electrical polarization switching of the P(VDF-TrFE) thin film. Furthermore, the fabricated device exhibits a memory window of ∼16.5 V, a high drain current on/off ratio of ∼105, a gate leakage current below ∼300 pA, and excellent retention characteristics for over 104 s. © 2014 AIP Publishing LLC.

Fabrication of ZnO and its enhancement of charge injection and transport in hybrid organic/inorganic light emitting devices

ZnO nanocrystals were synthesized by hydrolysis in methanol. X-ray diffraction and photoluminescence spectra confirm that good crystallized ZnO nanoparticles were formed. Utilizing those ZnO nanoparticles and poly [2- methoxy-5 - (3',7'-dimethyloctyloxy)- 1,4-phenylenevinylene] (MDMO-PPV), light emitting devices with indium tin oxide (ITO)/poly(3,4-oxyethyleneoxy-thiophene):poly(styrene sulfonate) (PEDOT:PSS)/ ZnO:MDMO-PPV/Al and ITO/PEDOT:PSS/MDMO-PPV/Al structures were fabricated. Electrolummescence (EL) spectra reveal that EL yield of hybrid MDMO-PPV and ZnO nanocrystals devices increased greatly as compared with pristine MDMO-PPV devices. The current-voltage characteristics indicate that addition of ZnO nanocrystals can facilitate electrical injection and charge transport. The decreased energy barrier to electron injection is responsible for the increased efficiency of electron injection. (c) 2007 Elsevier B.V. All rights reserved.

可生物降解脂肪族聚酯的反应接枝与相形态

聚（β-轻基丁酸醋-co-β-经基戊酸酷）（PHBV）是一种生物降解脂肪族聚酷，其结晶成核密度低，结晶速度比较慢且易生成大尺寸的球晶。以球晶中心向外扩展形成许多圆环状的开裂以及沿球晶生长方向形成许多劈裂，从而导致了PHBV呈脆性断裂。只要能有效地降低其结晶度，减小球晶尺寸，就可以达到增韧的目的。通过PHBV与二氧化碳一环氧丙烷共聚物（PPC）反应接枝来调控PHBV的结构和相形态，具有实际的理论意义和应用前景。开展了PPC的封端和与PHBv的接枝反应。首次提出了甲基丙烯酸缩水甘油醋（GMA）与PHBV及PPC与PHBV－GMA的接枝反应机理。确信PHBV接枝GMA的接枝点发生在PHBV骨架上的季碳原子上，反应过程中没有交联反应和降解反应的发生。发现PHBv-g-Gh1A共聚物上环氧基能与封端的PPc上的梭基熔融反应原位生成了PHBv-g-PPC共聚物。在机械共混物中两大分子之间的接枝和醋交换反应几乎不发生。GMA的引入阻止了PHBV的降解行为，从而改善了PHBV的加工性能。成功地调控了PHBVPC结构及相形态。证实了PHBV与PPC在反应共混过程中的接枝反应。加入PPC阻碍了PHBV的结晶，这在反应体系中更加明显。通过控制反应条件和反应物的组成，可以使非反应共混物中PHBV球晶变得不规则，发生扭曲变形，球晶尺寸降低；而在反应共混物中，可以使其球晶已很难辨认。SEM结果表明在PHBV用PC（30／70）和PHBV用PC（70／30）共混物中发生了相转变。尤其在反应共混物中淬断面表现为塑性。力学性能随共混组成而发生较大幅度的改变。发现通过改变组成及对反应共混相结构的控制，PHBV共混物的断裂伸长率可变化1一2个数量级，从而实现了制得一系列从脆性断裂塑料到高韧性弹性体的高分子材料。研究了反应接枝共混体系的熔融、结晶行为、等温和非等温结晶动力学。发现加入的GMA对PHBV有成核作用。引入的PPC阻碍了PHBV的结晶，降低PHBV的结晶度，球晶径向生长速率，平衡熔点和结晶能力。结晶速率与冷却速率有较大的依赖性。修正的Avrami方程能很好地描述PHBv和PHBv爪PC共混物非等温结晶过程。对动态力学性能的分析发现，反应共混物相比于非反应共混物聚合物玻璃化温度都有不同程度的内移，说明两组分间相容性增加，接枝共聚物具有良好的增容效果，显著地改善了两相界面性能。PHBV可以部分进入PPC相区，使共混物分子运动特征发生改变。发现在熔体加工条件下，PHBV与PPC之间很难发生酷交换反应，但是以辛酸亚锡为催化剂，氯苯为溶剂，在120℃条件下，两者可以发生醋交换反应。在聚己内醋（PCL）用PC熔融共混过程中GMA可以有效地抑制过氧化二异丙苯（DCP）所引起的PCL交联反应。在DCP和OMA存在下得到的样品之球晶具有十字消光现象，球晶规整度增大。同在溶液中醋交换催化剂存在下PPC和PCL发生了酷交换反应后所形成的球晶相结构相类似，而PCL／PPCOCP体系所形成的球晶中含有大量的非晶相区。从而，确信了GMA在脂肪族聚醋，脂肪族聚碳酸醋等生物降解高分子反应共混体系中的双重作用：一是引入具有高反应活性的官能团；二是减少在过氧化物作用下PHBV类高分子的降解及PCL类高分子的交联反应。PCL共混组分可以提高PPC相区的稳定性。提高反应时间或催化剂浓度同样能够改善热稳定性。

稀土三元催化剂下二氧化碳/环氧丙烷/缩水甘油醚共聚物的合成与性能研究

为拓宽PPC的应用范围，本论文在CO2与PO的共聚反应中，引入第三单体缩水甘油醚（烯丙基缩水甘油醚AGE、丁基缩水甘油醚BGE和苯基缩水甘油醚GPE），制备得到不同结构和性能的二氧化碳共聚物。主要工作总结如下：1．在CO2与PO的共聚反应中，引入第三单体 AGE，合成了侧链带双键的官能化二氧化碳共聚物Pol（PO-co-CO2-co-AGE）；2．在CO2-PO-BGE的共聚反应中，控制PO／B GE的摩尔比，可制得不同结构和 性能的二氧化碳共聚物Poly（P0-co-CO2-co-BGE），其Tg为-26.8-36.1℃，大幅度拓展了二氧化碳共聚物的最低使用温度区间；3．在CO2与PO的共聚反应中，引入第三单体GPE，合成了侧链带刚性苯环的 二氧化碳共聚物Poty（PO-co-CO2-co-GPE），提高了聚合产物的热稳定性。

胆甾液晶/聚合物混合体系结构与性质的研究

采用自由基聚合的方法分别合成了一系列不同共聚组成和不同分子量的MMA－n-BMA共聚物。通过偏光显微镜，DSC、X-射线衍射，电子显微镜以及扭辩分析等手段研究了ChN/poly（MMA－co－BMA）体系的相溶性，结构形态及其液晶性质，考察了共聚物结构因素对体系性质的影响。对多组分胆甾液品／聚合物体系的情况也进行了部分研究。研究表明：在一定组成范围内ChN/poly(MMA-co-BMA)体系具有一般的胆甾液晶性质。聚合物组分对ChN的结晶性具有明显的抑制作用，并最终导致了部分ChN组成S_A相的冻结。在多组分胆甾液晶的PDLC体系中，共聚物组分可以明显地提高体系液晶相的稳定性。另外，合成了胆甾液晶单体ChA，对其结构及液晶性质进行了表征和研究，并偿试了ChA-n-BMA共聚物的制备及其液晶性质的研究。发现在一定条件下，上述不完全聚合体系中的Ch相结构可以冻结在室温下。上述两种体系具有作为存貯材料的可能性。

甲基丙烯酸三苯甲酯不对称共聚行为研究

本论文首次利用共聚合方法获得了在常温下具有光活性的螺旋链共聚物，利用手性配体（-）SP、（+）DDB能合成光活性PTrMA和PDPAA。它们是具有稳定单手螺旋构象的聚合物。研究了不同手性配体对小位阻单体MMA阴离子聚合过程的立体控制作用，并对TrMA与MMA，DPAA与MMA及TrMA与DPAA各组单体在不同手性配体作用下的不对称阴离子共聚合行为进行了研究，提出了螺旋选择不对称聚合的概念。1，首次研究了手性配体（-）SP和（+）DDB对MMA阴离子聚合产物的立体构型的不同影响，利用~1HNMR谱表征了产物结构，发现在手性配体（-）SP存在下，以BuLi, t-BuLi及FLLi引发MMA聚合都得到高间同立构产物，引发剂中烷基阴离子位阻增大，间同立构含量增加。2，进行了MMA对TrMA的螺旋诱导，用不同的手性配体作用下获得的PMMA螺旋活性链在低温下引发TrMA聚合，得到了具有不同旋光方向的poly(MMA-co-TrMA)嵌段共聚物。从而证明了，MMA这种小位阻单体的聚合物虽然在常温下溶液中无法保持螺旋构象，但在低温下溶液中具有螺旋构象。并首次确定了不同手性配体作用下生成的PMMA单手螺旋链的方向。3，首次研究了不同手性配体存在下甲苯溶液中TrMA/MMA和DPAA/MMA及TrMA/DPAA共聚行为。表明不同方向的螺旋链能够选择与它本身立体结构适合的单体进行聚，即在不对称共聚合中存在着螺旋选择。螺旋选择不对称聚合现象的根源在于手性配体对聚合过程的立体指导作用。

Temperature Dependence of Surface Composition and Morphology in Polymer Blend Film

Thin films of poly(methyl methacrylate) (PMMA) and poly(styrene-ran-acrylonitrile) (SAN) blend can phase separate upon heating to above its critical temperature. Temperature dependence of the surface composition and morphology in the blend thin film upon thermal treatment was studied using in situ X-ray photoelectron spectroscopy (XPS) and in situ atomic force microscopy (AFM). It was found that in addition to phase separation, the blend component preferentially diffused to and aggregated at the surface of the blend film, leading to the variation of surface composition with temperature. At 185 degrees C, above the critical temperature, the amounts of PMMA and SAN phases were comparable.

Composition effect on dewetting of ultrathin films of miscible polymer blend

Two kinds of dewetting and their transition induced by composition fluctuation due to different composition in blend [poly(methyl methacrylate) (PMMA) and poly(styrene-ran-acrylonitrile) (SAN)] films on SiOx substrate at 145 degrees C have been studied by in-situ atomic force microscopy (AFM). The results showed that morphology and pathway of dewetting depended crucially on the composition. Possible reason is the variation in intensity of composition fluctuation resulted from the change of components in polymer blend. Based on the discussion of this fluctuation due to the composition gradient, parameter of U-q0/E, which describes the initial amplitude of the surface undulation and original thickness of film respectively, has been employed to distinguish the morphologies of spontaneous dewetting including bicontinuous structures and holes.

Synthesis and self-assembly of a novel Y-shaped copolymer with a helical polypeptide arm

novel biodegradable Y-shaped copolymer, poly(L-lactide)(2)-b-poly(gamma-benzyl-L-glutamic acid) (PLLA(2)-b-PBLG), was synthesized by the ring-opening polymerization (ROP) of N-carboxyanhydride of gamma-benzyl-L-glutamate (BLG-NCA) with centrally amino-functionalized poly(L-lactide), PLLA(2)-NH2, as a macroinitiator in a convenient way. The Y-shaped copolymer and its precursors were characterized by H-1 NMR, FT-IR, GPC, WAXD and DSC measurements. The self-assembly of the PLLA(2)-b-PBLG copolymer in toluene and benzyl alcohol was examined. It was found that the self-assembly of the copolymer was dependent on solvent and on relative length of the PBLG block. For a copolymer with PLLA blocks of 26 in total degree of polymerization (DP), if the PBLG block was long enough (e.g., DP = 54 or more), the copolymer/toluene solution became a transparent gel at room temperature. In benzyl alcohol Solution, only PLLA(2)-b-PBLG containing ca. 190 BLG residues could form a gel: those with shorter PBLG blocks (e.g., DP = 54) became nano-scale fibrous aggregates and these aggregates were dispersed in benzyl alcohol homogeneously.

Incorporation of Nanoparticles into Polyelectrolyte Multilayers via Counterion Exchange and in situ Reduction

We report a general method for incorporation of nanoparticles into polyelectrolyte multilayer (PEM) thin films by utilizing the excess charges and associated counterions present in the PEMs. Silver ions were introduced directly into multilayers assembled from poly(diallyldimethylammonium chloride) (PDDA) and poly(styrene sulfonate) (PSS), (PDDA/PSS)(n), by a rapid ion exchange process, which were then converted into silver nanoparticles via in situ reduction to create composite thin films. The size and the content of the nanoparticles in the film call be tuned by adjusting the ionic strength in the polyelectrolyte solutions used for the assembly. Spatial control over the distribution of the nanoparticles in the PEM was achieved via the use of multilayer heterostructure containing PDDA/PSS bilayer blocks assembled at different salt concentrations. Because excess charges and counterions are always present in any PEM, this approach can be applied to fabricate a wide variety of composite thin Films based on electrostatic self-assembly.

Solvent-induced Morphology of the Binary Mixture of Diblock Copolymer in Thin Film: The Block Length and Composition Dependence of Morphology

A series of binary SB blend samples with various overall volume fraction of PS (Phi(PS)) and different discrete distribution of the block length (denoted as d(PS) or d(PB)) were prepared by mixing various asymmetric poly(styrene)-block-poly(butadiene) (SB) block copolymers with a symmetric SB block copolymer. The influences of the external solvent field, composition, and the block length distribution on the morphologies of the blends in the thin films were investigated by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The experimental results revealed that after solvent annealing, the interface of the blend thin films depended mainly on the cooperative effects of the annealing solvent and the inherently interfacial curvature of the blends. Upon exposure to the saturated vapor of cyclohexane, which has preferential affinity for the PB block, a "threshold" of Phi(PS) (approximate 0.635-0.707) was found. Below such threshold, the influence of the annealing solvent played an important role on the interfacial curvature of the blend thin film.