Phosphonated poly(1,6-heptadiyne) derivatives prepared by metathesis polymerization for nonlinear optics

Summary Poly(triethyldipropargylphosphonoacetate) (TDPA), poly[(tetraethyl dipropargylmethylenediphosphonate) (TDMDP) were prepared by metathesis polymerization using transition-metal catalysts. MoCl₅-based catalyst systems were more effective for the polymerization of these monomers than WCl₆-based catalyst systems. Resulting polymers exhibited good solubility in common organic solvents and could be easily cast on glass plates to give thin films. Third-harmonic Maker fringe technique was used to measure third-order nonlinear susceptibility,x ⁽³⁾, for thin film of poly(TDPA). Thex ⁽³⁾ was evaluated to be 3.4x10^-11 esu at incident wavelength of 1.907m.     

Course of conducting poly(1,6-heptadiyne) formation through ultraviolet–visible spectroscopy

Polymerization of the symmetrical non-conjugated diyne, 1,6-heptadiyne, was carried out in nitrogen atmosphere with different initiators in dimethyl formamide. The course of polymerization was followed through ultraviolet–visible spectroscopy. The rate of polymerization was determined under different conditions and used for comparing the efficiency of the initiators. The poly(1,6-heptadiyne) was isolated and characterized through infrared spectroscopy, conductivity measurements and cyclic voltammetry. The electroactivity of the polymer was revealed.     

Kinetics of oxygen doping and oxidation of poly(1,6-heptadiyne), a conducting polyene

The oxidative stability of poly(1,6-heptadiyne) (a free-standing dopable polyene) has been studied via conductivity measurements. A kinetic model of degradation has been applied to the results and it has been shown that the degradation is first order with an activation energy of ～ 13 kcal mol¹. It is also shown that solvent wash during polymerization affects degradation rate but not activation energy. Simultaneous oxygen uptake-conductivity experiments are also described. The effect of light on degradation rates is presented. Results of these experiments are compared with earlier work on polyacetylene.     

Achieving efficient poly(3,4-ethylenedioxythiophene)-based supercapacitors by controlling the polymerization kinetics

In this study, we have prepared a series of poly(3,4-ethylenedioxythiophene) (PEDOT) with various molecular weight by using an inhibitor, imidazole (Im). The X-ray diffraction (XRD) results show that the PEDOT with larger molecular weight enhances the polymer chain ordering and stacking which leads to higher conductivity. With increasing the amount of Im, the conductivity of PEDOT can be increased from 4.01 S cm⁻¹ (Im = 0.0 M) to 153.6 S cm⁻¹ (Im = 1.8 M). Comparisons of the cyclic voltammetry (CV), it enables correlation between the conductivity and specific capacitance, which is important for understanding the electrochemical capacitive behavior of conjugated polymer for pseudo-capacitor application. The PEDOT prepared with 1.8 M Im shows a specific capacitance of 124 F g⁻¹, which is 2.2 times larger than the one without Im (57 F g⁻¹).     

Stabilization of higher-order structure of poly(phenyleneethynylene)s by metathesis polymerization at the side chains

Novel poly(m-phenyleneethynlene-p-phenyleneethynylene)s bearing polymerizable diene or norbornene groups were synthesized by the Sonogashira–Hagihara coupling polymerization of the corresponding d-hydroxyphenylglycine-derived diiodo monomers with p-diethynylbenzene. These polymers exhibited strong Cotton effects derived from a predominantly one-handed helical conformation in CHCl₃ and tetrahydrofuran, but exhibited weak or no Cotton effects in N,N-dimethylformamide. The metathesis polymerization of the diene and norbornene moieties was performed at the side chains of the polymers under diluted conditions in the presence of a chain-transfer agent, if necessary. The reaction took place intramolecularly, which was confirmed by size exclusion chromatography (SEC) measurements. The polymers exhibited stronger Cotton effects even in polar media after the intramolecular crosslinking, which indicated stabilization of the predominantly one-handed helical structures.     

Synthesis and characterization of hydrogenated poly(norbornene endo-dicarboximide)s prepared by ring opening metathesis polymerization

Poly(norbornene imide)s prepared by ring opening metathesis polymerization (ROMP) have been generally synthesized from 5-norbornene-exo,exo-2,3-dicarboximides (exo-NDIs), since 5-norbornene-endo,endo-2,3-dicarboximides (endo-NDIs) exhibit considerably lower reactivity toward conventional ROMP catalysts as compared with exo-NDIs. Therefore, there has been limited information on poly(endo-NDI)s, although the endo-stereoisomer monomers are the principal products in Diels–Alder reaction between cyclopentadiene and maleimides. Here we synthesized various poly(endo-NDI)s using available Grubbs catalysts, and subsequently hydrogenated their backbone double bonds to obtain high molecular weight samples with M_n > 150,000. The thermal, thermo-mechanical, mechanical, and optical properties of poly(endo-NDI)s before and after hydrogenation were then investigated, together with the structural properties by wide-angle X-ray scattering and refractive index, in comparison with those of the corresponding poly(exo-NDI)s. Surprisingly, poly(endo-NDI)s exhibit significantly higher glass transition temperatures (by ca. 34 °C) and refractive index values than the exo-counterparts, probably due to increased intermolecular packing. Other properties such as thermal stability, tensile modulus, coefficient of thermal expansion, optical transparency, water absorption, and water transmission rate are quite comparable. Overall, convenient monomer preparation coupled with attractive physical properties makes poly(endo-NDI)s very interesting for practical applications such as optical films and flexible substrates for optoelectronics.     

Phase separation in poly(butylene terephthalate)-based materials prepared by solid-state modification

The morphology of a series of poly(butylene terephthalate) (PBT)/fatty acid dimer diol (FADD)-based copolyesters prepared by solid-state modification (SSM) was studied. It was shown that in copolyesters containing less than 10 wt% FADD two different phases, i.e. a PBT crystalline phase and a PBT-rich amorphous phase, are present. The FADD residues were more or less homogeneously distributed throughout the interlamellar regions. For copolymers containing more than 10 wt% of FADD, a three-phase morphological model has to be used due to phase separation of a FADD-rich amorphous phase from the PBT-rich matrix, as confirmed by solid-state nuclear magnetic resonance spectroscopy and transmission electron microscopy. The final morphology was dependent on the morphology of the PBT/FADD-based physical mixtures prior to SSM. In addition, it was shown that FADD diffusion during SSM influences the final morphology.     

A novel approach for synthesis of poly(norbornene)‐co‐poly(styrene) block copolymers via metathesis polymerization and free‐radical polymerization

It is successfully realized that block copolymers are synthesized via metathesis polymerization followed by free‐radical polymerization. This method is performed using styrene (St) and norbornene, one block is synthesized using the Grubbs second generation catalyst in the presence of chain transfer agents, and the subsequent polymerization of St is initiated by azo compounds to complete the additional blocks in the copolymers. The use of free‐radical polymerization instead of controlled radical polymerization or ionic polymerization can be potentially superior for industrialization. As a result, the molecular weights of the block copolymers ranging from 10.4 to 54.3 kDa and polydispersity indices ranging from 1.30 to 1.91 are obtained. In principle, this new method can be potentially useful to prepare a broad range of block copolymers with cyclic olefin groups in the main chains, which may be used in some particular applications.     

Surface properties of poly(dimethylsiloxane)-based inorganic/organic hybrid materials

Poly(dimethylsiloxane) (PDMS)-based hybrid materials were prepared by the sol-gel method on Si wafers, Al and polystyrene (PS) substrates. The reaction was monitored by attenuated total reflectance-infrared (ATR-IR) spectroscopy. The hybrid materials have always one surface made in contact with air and one with a substrate. These surfaces were investigated by using tapping mode atomic force microscopy (AFM), X-ray photo-electron spectroscopy (XPS), low-energy ion scattering (LEIS) and dynamic contact angle (DCA) analysis. The hybrid sample surfaces made in contact with air and substrates appeared to have different structures. The former have a silica-free PDMS top layer of ∼2 nm thick; while in the latter cases, SiO₂ are located at or just beneath the outermost atomic layer. In air and at room temperature, SiO₂ are likely beneath the outermost atomic layer. In contact with water, polar -OH groups at the surface of SiO₂ can easily stretch out to the outermost atomic layer. No correlation was found between the roughness of the surfaces and the amount of in situ formed SiO₂ present in the materials.     

New azo-chromophore-containing multiblock poly(butadiene)s synthesized by the combination of ring-opening metathesis polymerization and click chemistry

A combination of ring-opening metathesis polymerization (ROMP) and click chemistry approach was utilized for the first time in preparation of multiblock copolymers. The dibromo-functionalized telechelic poly(butadiene) (PBD) was synthesized firstly by ROMP of 1,5-cyclooctadiene in the presence of a symmetrical difunctional chain transfer agent and transformed into diazido-telechelic PBD, which was then reacted with a dialkynyl-containing azobenzene chromophore via click reaction, producing novel multiblock PBDs collected by azobenzene groups and newly formed triazole moieties. The monomer and polymer were characterized by IR, UV-vis, LC/MS, and NMR techniques. The produced multiblock copolymers have molecular weights within 13.3 and 57.8 kDa, and their polydispersity indices ranging from 1.98 to 2.38 by gel permeation chromatography measurement. The multiblock PBDs containing azo chromophores and triazole moieties with or without hydrogen-bonding interreaction with 4,4′-dihydroxybiphenyl molecule exhibited different photoisomerization efficiency from trans to cis as observation in UV-vis spectroscopy. The morphologies of multiblock PBDs were also investigated by atom force microscopy.     

Synthesis of poly(cyclooctene) by ring‐opening metathesis polymerization: Characterization and shape memory properties

Cis‐cyclooctene was polymerized via ring‐opening metathesis polymerization using a well‐defined ruthenium catalyst (Grubbs' type) under varying reaction conditions. Control over molecular weight was achieved by the inclusion of a chain transfer agent and its influence on the behavior of the obtained polymers was evaluated. The resulting polymers were characterized by means of differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis. Taking into account their thermal behavior, samples of appropriate molecular weight were subjected to a suitable treatment by chemical crosslinking to obtain a material showing thermally induced shape memory effect. The material recovers its original shape after several cycles of deformation into different shapes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

降冰片烯类聚合物用于离子交换膜的研究进展

离子交换膜作为燃料电池以及液流电池的核心部件, 对电池的性能起着关键作用。由于开环易位聚合的降冰片烯类聚合物其主链中保留着双键, 而具有优越热稳定性和良好的可加工性, 逐渐成为离子交换膜材料的研究热点。本文综述了近年来基于开环易位聚合的降冰片烯类聚合物用于阳离子交换膜、阴离子交换膜和复合离子交换膜的研究状况, 分析了膜的结构组成与性能测试, 并与Nafion的性能进行了比较, 展望了降冰片烯类聚合物在离子交换膜领域的发展趋势。     

The effect of a free radical quencher on the conductivity,oxidative stability and free radical population of poly(1,6-heptadiyne)

The effect of a free radical quencher on the intrinsic properties of poly(1,6-heptadiyne) has been studied. It is shown that this treatment reduces the number of free radicals, lowers the conductivity while leaving the transport barriers unchanged and reduces the susceptibility of the material to oxidation. These effects are discussed in terms of hydrogen atom transfer chemistry.     

Reversible chain transfer catalyzed polymerization (RTCP): A new class of living radical polymerization

This article introduces the new family of living radical polymerizations with germanium (Ge), tin (Sn), phosphorus (P), and nitrogen (N) catalysts which we recently developed. The polymerizations are based on a new reversible activation mechanism, Reversible chain Transfer (RT) catalysis. Low-polydispersity polymers are obtained in the homopolymerizations and random and block copolymerizations of styrene, methyl methacrylate, and functional methacrylates. The background, performance, and kinetic features of the polymerizations are described. Attractive features of the catalysts include their high reactivity, low toxicity (Ge, P, and N), low cost (P and N), and ease of handling (robustness).     

Enzyme-catalyzed syntheses of poly(1,6-hexanediyl isophthalate) and poly(1,6-hexanediyl terephthalate) in organic medium

Summary The enzyme-catalyzed synthesis of poly(1,6-hexanediyl terephthalate) and poly(1,6-hexanediyl isophthalate) is described. An unsuccessfull attempt to synthesize poly(1,6-hexanediyl o-phthalate) is also presented and the reactivity of those three monomers is discussed according to the enzymatic nature of the catalyst. The crude polyesters are characterized by ¹H and ¹³C NMR spectroscopy and by differential scanning calorimetry. Macrocycles are isolated from poly(1,6-hexanediyl isophthalate) and characterized by steric exclusion chromatography and by mass spectrometry. The number-average molar masses and the thermal properties of the crude, linear and cyclic polyesters are also reported.     

A new class of transparent polymeric materials. III. Miscible blends of poly(N-methylmaleimide-alt-isobutene) with poly(acrylonitrile-co-styrene) and the properties of the blends

The blend miscibility of poly(N-methylmaleimide-alt-isobutene) [poly-(MeMI-IB)] with poly(acrylonitrile-co-styrene) (SAN) was investigated by means of measurement of the glass transition temperature of the blends. Poly(MeMI-IB) was found to be miscible with SAN of a specific range of acrylonitrile (AN) contents in the copolymer to produce transparent moldings. The refractive index changed from 1.58 to 1.53 and the dispersion decreased with increasing the amount of poly(MeMI-IB) in the blends. The stress optical coefficient of poly(MeMI-IB) was found to be reduced by the blending of SAN. The glass transition temperature, flexural modulus, and surface hardness of the blends increased with an increase in the amount of poly(MeMI-IB) in the blend. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 925–929, 1997     

Ring-opening metathesis polymerization (ROMP) of norbornenyl-functionalized fatty alcohols

Novel biorenewable-based thermosets have been successfully synthesized by the ring-opening metathesis polymerization (ROMP) of norbornenyl-functionalized fatty alcohols derived from soybean oil (NMSA), Dilulin (NMDA), ML189 (NMMA) and castor oil (NMCA). The effects of the monomer structure on the polymerization process, and the thermal and mechanical properties of the resulting thermosets have been extensively investigated. The number of ROMP-reactive rings appended to the fatty acid chain and the viscosity play an important role in controlling the initiation and propagation processes of the polymerization and the final properties of the thermosets obtained. The thermosets have been characterized by Soxhlet extraction, DMA, TGA, and tensile tests. It has been found that polyNMDA and polyNMMA have best thermo-mechanical properties. Compared with polyNMSA, the polyNMDA and polyNMMA thermosets exhibit lower soluble fractions, and higher thermal stabilities and mechanical properties, because of more effective crosslinking; whereas, polyNMCA exhibits a higher soluble fraction, and lower thermal stability, resulting from incomplete polymerization of the more viscous NMCA monomer.     

Monodisperse poly(p-chloromethylstyrene) microbeads by dispersion polymerization

In this study, an alternative dispersion polymerization method for the para isomer of chloromethylstyrene was proposed. Highly monodisperse poly(p-chloro-methylstyrene) (PCMS) particles in the size range of 1.67–3.75 μm were obtained. The monodispersity and the isolation yield of PCMS particles were significantly improved relative to the methods available in the literature. Azobisisobutyronitrile and polyacrylic acid were selected as the initiator and the steric stabilizer, respectively, in the dispersion medium composed of ethanol and methoxyethanol. The results indicated that the particle size increased with increasing initiator concentration. An increase in the stabilizer concentration led to a decrease in the particle size. The methoxyethanol/ethanol ratio was found as one of the most important parameters controlling the average size and the size distribution. Contrary to the tendencies noted in the literature, the particle size decreased with increasing polymerization temperature.     

Effect of functionalized MWCNTs on the thermo-mechanical properties of poly(5-ethylidene-2-norbornene) composites produced by ring-opening metathesis polymerization

Functionalized multiwalled carbon nanotubes (MWCNTs) reinforced poly(5-ethylidene-2-norbornene (ENB)) composites have been fabricated via ring-opening metathesis polymerization. Verification of covalent bond formation between the functionalized carbon nanotubes and the polyENB matrix was demonstrated by solvent exposure followed by thermal gravimetry. The tensile toughness of the composites increased by 300% with dramatic morphological changes on the resulting fracture surfaces when just 0.8 wt% norbornene-functionalized MWCNTs (f-MWCNTs) were added to the polymer. A slight increase of glass-transition temperature was observed by dynamic mechanical analysis compared to a decreased value with unfunctionalized MWCNTs.