Syntheses and characterizations of new copolymers of vinylidene cyanide with para substituted α acetoxystyrenes

Summary Vinylidene cyanide has been copolymerized in solution by radical reaction with equal initial mole fraction of para substituted acetoxystyrenes. The copolymers have been characterized by means of DSC, TGA and GPC. These products are stable up to 220° and have no visible glass transition temperature. The microstructure of these new copolymers has been studied by ¹³CNMR; they have an alternating structure and monomers units are arranged in head-to-tail placements.     

Synthesis and characterization of novel crown ether containg copolymers Ru catalyzed copolymerization of 4′-acetylbenzocrown ethers with α,ω-dienes

Summary Ruthenium catalyzed step growth copolymerization of 4-acetylbenzo-15-crown-5 and 4-acetylbenzo-18-crown-6 and ,-dienes such as 1,3-divinyltetramethyldisiloxane or 3,3,6,6-tetramethyl-3,6-disila-1,7-octadiene give novel copolymers which incorporate crown ethers into the polymer backbone in a regular manner. The synthesis of these thermally stable copolymers and their characterization is reported. Lithium cation crown complexes have been formed.     

Effect of comonomer partitioning on the kinetics of mesophase formation in random copolymers of propene and higher α-olefins

The effect of counit type on the kinetics of mesophase formation has been investigated by means of chip-calorimetry in propene/α-olefin random copolymers, containing counits which show large differences in their co-crystallization behavior with propene, i.e. 1-butene and 1-hexene. Non-isothermal crystallization experiments indicated that the minimum cooling rate at which mesophase formation is observed is directly related to the kinetic of α-phase crystallization, which is lower for the copolymer with the bulkier 1-hexene counit. Isothermal structuring was probed in a wide temperature range, revealing that a double bell-shaped curve is required to describe the temperature dependence of crystallization times of the two polymorphs. The ordering kinetics of the mesophase is the fastest in i-PP homopolymer and decreases with increasing comonomer bulkiness, analogous to what happens for the monoclinic phase. The results are discussed by considering the effect of comonomer on the driving force for mesophase formation, also at the light of new WAXD and density evidences, which prove different extents of inclusion of 1-butene and 1-hexene in the ordered phases.     

Rheological,thermal and crystallisation properties of ethylene,propylene and α-olefin copolymers. I Rheological properties

Abstract

A series of random ethylene, propylene/1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene copolymers, ethylene and propylene homopolymers were prepared and investigated. The rheological properties (steady state and dynamic shear viscosity, creep compliance and plateau modulus), of copolymer samples with different co-unit content and molecular masses were determined and compared with the properties of homopolymers. The effects of the length of counit and the comonomer content were investigated. The copolymers exhibited similar rheological properties to the homopolymer but they have a lower shear viscosity, normal viscosity, higher steady state creep compliance and smaller plateau modulus values. The effect of comonomer content was evaluated on the bases of free volume theory.     

Synthesis of α,ω-hydroxyalkyl telechelic polydimethylsiloxane soft segments and preparation of waterborne polyurethane–polydimethylsiloxane block copolymers

In this paper, by optimizing synthesis process of α,ω-hydroxyalkyl telechelic polydimethylsiloxane, α,ω-bis(3-(1-methoxy-2-hydroxypropoxy)propyl)polydimethyl siloxane (PMTS), the yield of hydrosilylation product, 1,3-bis(glycidoxypropyl) tetramethyldisiloxane exceed 86.5%. By tracing the change of methanol (gravimetry) and measuring the change of molecular weights of polydimethylsiloxanes at different reaction time (titration), the optimum reaction time of methoxylation reaction and ring-opening polymerization was determined as 8 and 12 h. Using α,ω-bis(3-(1-methoxy-2-hydroxypropoxy)propyl)polydimethyl siloxane with different molecular weights, waterborne polyurethane–polydimethylsiloxane block copolymer were prepared. The influences of molecular weights and content of α,ω-hydroxyalkyl telechelic polydimethylsiloxane on the waterborne polyurethane–polydimethylsiloxane block copolymers were investigated in detail. The addition of α,ω-hydroxyalkyl telechelic polydimethylsiloxane could improve the water-resistance property obviously and increase the elongation at break. However, the mechanical property was reduced with increase of content and molecular weight of α,ω-hydroxyalkyl telechelic polydimethylsiloxane.     

Copolymerization of α-methylstyrene with N-alkylmaleimides

Summary Alternating copolymers of -methylstyrene (-MeSt) with N-alkylmaleimides (RMI; R=Et, n-Pr, iso-Pr, n-Bu, n-Hex) were prepared in Calvet differential microcalorimeter under different monomer-to-monomer ratios in the feed using AIBN as initiator. The equilibrium constants of CT-complex monomers have low values: 0.02–0.05 L.mol^-1 but the mechanism of copolymerization indicates the participation of CT-complex. Equilibrium constants and rate of decomposition under the TGA conditions are not dependent on steric factors, but the rate of copolymerization decreases with the increase of bulkiness of alkyl substituent. In high conversion copolymerization it was observed that in the presence of an excess of homopolymerizable RMI, alternating copolymers are quantitatively formed prior to the formation of poly(RMI).Dedicated to Professor Dragutin Fle on the occasion of his 70th birthday     

Microwave-assisted reactions of α-diazoketones with hetaryl and ferrocenyl thioketones*

Differently substituted hetaryl thioketones react with less reactive diazoketones under microwave (MW) irradiation in toluene solution. After only 2?min, the reactions were complete and, depending on the type of the used diazoketone, α,β-unsaturated ketones, acyl substituted thiiranes or 1,3-oxathioles were obtained as final products. In the case of azibenzil and di(thiophen-2-yl) thioketone, a new type of 1,5-dipolar electrocyclization of the intermediate thiocarbonyl ylide involving a thiophene ring led to a fused sulfur heterocycle. In contrast to hetaryl thioketones, the ferrocenyl analogues decompose under MW irradiation. Alternatively, they react with diazopropanone and 2-diazo-1-phenylethanone in boiling THF in the presence of LiClO₄ to give α,β-unsaturated ketones as sole products. In these cases, the reactions require long reaction times.     

Inhibitory Activities of Cyanidin and Its Glycosides and Synergistic Effect with Acarbose against Intestinal α-Glucosidase and Pancreatic α-Amylase

Cyanidin and its glycosides are naturally dietary pigments which have been indicated as promising candidates to have potential benefits to humans, especially in the prevention and treatment of diabetes mellitus. We investigated the structure activity relationships of cyanidin and its glycosides to inhibit intestinal α-glucosidases and pancreatic α-amylase in vitro. The results found that cyanidin and its glycosides are more specific inhibitors of intestinal sucrase than intestinal maltase. Cyanidin-3-galactoside and cyanidin-3-glucoside were the most potent inhibitors against intestinal sucrase and pancreatic α-amylase with IC(50) values of 0.50 ± 0.05 and 0.30 ± 0.01 mM, respectively. Our findings indicate that the structural difference between glucose and galactose at the 3-O-position of cyanidin was an important factor for modulating the inhibition of intestinal sucrase and pancreatic α-amylase. The combination of cyandin-3-glucoside, cyanidin-3- galactoside or cyanidin-3,5-diglucosides with a low concentration of acarbose showed synergistic inhibition on intestinal maltase and sucrase. The synergistic inhibition was also found for a combination of cyanidin or cyanidin-3-glucoside with a low concentration of acarbose. The findings could provide a new insight into a use for the naturally occurring intestinal α-glucosidase and pancreatic α-amylase inhibitors for the prevention and treatment of diabetes and its complications.     

Microstructure of copolymers of vinylidene cyanide,methacrylonitrile and acrylonitrile with methyl α acetoxyacrylate,a captodative monomer

Summary Copolymers of vinylidene cyanide (1a) methacrylonitrile (1b) and acrylonitrile (1c) with a captodative monomer, methyl acetoxyacrylate were synthesized by radical copolymerization and their microstructures were studied by ¹³C NMR spectroscopy.The copolymer of 1a with methyl -acetoxyacrylate (2) has mostly an alternating structure but the copolymers of 1b and 1c with 2 are rather statistical. The measurement of their reactivity ratios for these two reactions is in agreement with the proposed structures.     

Polynorbornene copolymers with pendent o-carborane and carbazole groups: Novel side-chain donor–acceptor copolymers for turn-on sensing of nucleophilic anions

Vinyl-type polynorbornene copolymers with side-chain o-carborane (1-phenyl-o-carborane for P1–P3; 1-methyl-o-carborane for P4) and carbazole moieties were produced by vinyl addition copolymerization of norbornene monomers using a Pd(II) catalyst in combination with 1-octene chain transfer agent. The catalytic system provided well-defined copolymers with controlled incorporation of monomers. The copolymers possessed high thermal stability with high decomposition (T_d5 > 410 °C) and glass transition temperatures (T_g > 350 °C). Treatment of the closo-copolymers (P1–P4) with excess KOH in refluxing EtOH/THF led to degradation of the closo-carborane cage to produce nido-copolymers (nido-(P1–P4)). While P1–P3 exhibited a weak carbazole-based fluorescence, the corresponding nido-copolymers gave rise to a 2.0–3.6-fold increase in PL intensity depending on the comonomer content. An electrochemical study and comparative PL results of P4 and nido-P4 suggest that photoinduced charge transfer from carbazole donors to 1-phenyl-o-carborane acceptors was responsible for the weak fluorescence of P1–P3.     

Syntheses of diblock copolymers: poly(2-methylpropene)-b-poly(α-amino acid)

Summary Diblock copolymer poly (2-methylpropene)-b-poly (-amino acid) was obtained by polymerization of the corresponding N-caboxy anhydride initiated by a poly (2-methylpropene) bearing a terminal amine in dioxane/CH₂Cl₂ mixture. Copolymers were analyzed by FT IR, ¹H and ¹³C NMR. of the -amino acid segment determined by ¹H NMR fits well with those obtained by a theoretical calculation.     

Tissue Distribution of α- and γ-Tocotrienol and γ-Tocopherol in Rats and Interference with Their Accumulation by α-Tocopherol

The aim of this study was to evaluate tissue distribution of vitamin E isoforms such as α- and γ-tocotrienol and γ-tocopherol and interference with their tissue accumulation by α-tocopherol. Rats were fed a diet containing a tocotrienol mixture or γ-tocopherol with or without α-tocopherol, or were administered by gavage an emulsion containing tocotrienol mixture or γ-tocopherol with or without α-tocopherol. There were high levels of α-tocotrienol in the adipose tissue and adrenal gland, γ-tocotrienol in the adipose tissue, and γ-tocopherol in the adrenal gland of rats fed tocotrienol mixture or γ-tocopherol for 7 weeks. Dietary α-tocopherol decreased the α-tocotrienol and γ-tocopherol but not γ-tocotrienol concentrations in tissues. In the oral administration study, both tocopherol and tocotrienol quickly accumulated in the adrenal gland; however, their accumulation in adipose tissue was slow. In contrast to the dietary intake, α-tocopherol, which has the highest affinity for α-tocopherol transfer protein (αTTP), inhibited uptake of γ-tocotrienol to tissues including adipose tissue after oral administration, suggesting that the affinities of tocopherol and tocotrienol for αTTP in the liver were the critical determinants of their uptake to peripheral tissues. Vitamin E deficiency for 4 weeks depleted tocopherol and tocotrienol stores in the liver but not in adipose tissue. These results indicate that dietary vitamin E slowly accumulates in adipose tissue but the levels are kept without degradation. The property of adipose tissue as vitamin E store causes adipose tissue-specific accumulation of dietary tocotrienol.     

Construction of inter-chain polymers and the investigation into Friedel–Crafts alkylation of styrene–acrylonitrile copolymers with chloroprene rubber and characterization

In this study, the Friedel–Crafts alkylation was realized in a solvent free processing of styrene–acrylonitrile copolymers/chloroprene rubber (SAN/CR) molten blending which contributes the formation of SAN-co-CR co-polymers and improved compatibility between SAN and CR. The properties of several Lewis acid compounds were tested as catalysts among which AlCl₃ was the most efficient. The effects of blending temperature and time on the co-polymer formation in situ were also investigated. The methodology of weighing and Fourier transform infrared analyses indicated that the reaction degree increases with increasing blending temperature and time in the ranges of this study. The micro-structures and reaction mechanisms of the resulted SAN-co-CR polymers and morphological structures of SAN/CR/AlCl₃ blends were characterized as well by differential scanning calorimetry, FT-IR spectra, GPC and scanning electron microscopy. The results showed that the inter-facial reactions between SAN and CR have been effectively improved. Moreover, the inter-chain structure of SAN-co-CR co-polymers was proposed which is different from general grafting or blocking co-polymers.     

Chaperone-like α-cyclodextrins assisted self-assembly of double hydrophilic block copolymers in aqueous medium

Chaperones are defined as a family of protein that mediates the correct assembly of other polypeptides but that are not components of the functional assembled structures. In this work, we have devised a novel method in which α-cyclodextrins (α-CDs), “artificial chaperones”, facilitate block copolymers self-assembling into the expected structure. Poly(ethylene oxide)-b-poly(4-vinylpyridine) (PEO₄₅-b-P4VP₇₀) is first threaded by α-CDs, leading to the formation of metastable micelles. After stabilizing the metastable micelles by shell cross-linking with poly(ethylene oxide)-b-poly(acrylic acid) (PEO₁₁₄-b-PAA₅₀), α-CDs are removed and the expected structure, polymeric vesicle, is achieved. On the contrary, only spherical micelles are formed in the similar conditions without the assistance of α-CD. Therefore, α-CDs, which act as chaperones, guide the self-assembly of block copolymers in the expected pathway.     

Physico-chemical,mechanical and cytotoxicity characterizations of Laponite®/alginate nanocomposite

Combining clay minerals containing silica with polymers can improve the performance of polymers in biomedical applications by the synergistic combination of physico-chemical and biological properties of both phases. In this study, Laponite® — a synthetic biocompatible and biodegradable silicate clay mineral, was combined with alginate to improve alginate mechanical and biological characteristics. The physico-chemical properties (porosity, degradation, swelling, crystalline structure, compressive strength, and injectability) and biological responses (cytotoxicity and cell morphology) of the Laponite/alginate nanocomposites were investigated in the study. The results showed that the incorporation of Laponite into alginate significantly enhanced alginate compression strength without hindering its injectability when the percentage of clay mineral was below 50%. The prepared clay polymer nanocomposites (CPN) were not toxic and the viability of cells cultured in its extract was indeed higher than alginate alone. However, these prepared CPN poorly supported cell adhesion, probably due to the high degradation rate of the materials.     

Blends of ethylene–octene copolymers with different chain architectures – Morphology,thermal and mechanical behavior

Blends of two elastomeric ethylene–octene copolymers with similar octene contents having a random (ORC) and a blocky architecture (OBC) are prepared by melt mixing. The thermal and mechanical properties of ORC, OBC and their blends are investigated by DSC, dynamic mechanical analysis and tensile tests. The morphology of the semi-crystalline samples is studied by AFM and WAXS. Two types of crystals have been observed: (i) Orthorhombic crystals forming lamellae with an estimated thickness of about 13 nm composed mainly of long polyethylene-like sequences of OBC that melt a temperature of about 120 °C and (ii) fringed micellar crystals with a thickness of 2–4 nm formed basically by short polyethylene-like sequences of ORC that have melting temperatures between 30 and 80 °C. The amorphous phase contains a relatively homogeneous mixture of segments of both components indicated by the relatively uniform shape of the loss modulus peaks from dymamic-mechanical measurements for all investigated copolymers and blends. ORC crystallization is hindered in blends as indicated by lower melting enthalpies. This might be related to the high octene content of the amorphous phase at the relevant crystallization temperature as well as geometrical constraints since ORC crystallization occurs in an already semi-crystalline polymer. The results of tensile tests show that the mechanical behavior can be tailored via blend composition and morphology of the semi-crystalline material. The findings clearly indicate that blending is a powerful strategy to optimize the properties of polyolefin-based copolymers.     

Syntheses and characterizations of two novel Ln(III)–Cu(II) coordination polymers constructed by Pyridine-2,4-dicarboxylate ligand

Two novel three dimension Ln(III)–Cu(II) coordination polymers [Gd₂Cu(pydc)₄(H₂O)₆]_n and [Sm₂Cu₃(pydc)₆(H₂O)₆]_n were prepared by the hydrothermal reactions of CuO, Ln₂O₃ (Ln = Gd, Sm), H₂pydc (H₂pydc = 2,4-pyridinedicarboxylic acid) and characterized by single-crystal X-ray diffraction analysis.     

Thermal conductivity of Ca α-SiAlON ceramics with varying m and n values

α-SiAlON is well known for its excellent mechanical properties, but its thermal properties are less investigated. In this work, we investigate the thermal conductivity of Ca α-SiAlON ceramics with varying m and n values and prepared samples by spark plasma sintering (SPS) at 1600°C or gas pressure sintering (GPS) at 1800°C and 1900°C. The prepared Ca α-SiAlON ceramics showed thermal conductivities ranging from 4.6 to 10.7 W/(mK) at 25°C. It was found that the thermal conductivity of the α-SiAlON samples could be reduced by increasing either m or n or both. Besides, the samples prepared by SPS had lower thermal conductivity compared with those by GPS due to their smaller grain size, and the effect of m and n would be minor after m reached 2. These results provide basic knowledge for tuning α-SiAlON's thermal conductivity for applications concerning thermal management.     

Preparation of pH-responsive membranes with amphiphilic copolymers by surface segregation method☆

Novel pH-responsive membranes were prepared by blending pH-responsive amphiphilic copolymers with pol-yethersulfone (PES) via a nonsolvent-induced phase separation (NIPS) technique. The amphiphilic copolymers bearing Pluronic F127 and poly(methacrylic acid) (PMAA) segments, abbreviated as PMAAn–F127–PMAAn, were synthesized by free radical polymerization. The physical and chemical properties of the blend membranes were evaluated by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectrum, water con-tact angle, Zeta potential and X-ray photoelectron spectroscopy (XPS). The enrichment of hydrophilic PMAA seg-ments on the membrane surfaces was attributed to surface segregation during the membrane preparation process. The blend membranes had significant pH-responsive properties due to the conformational changes of surface-segregated PMAA segments under different pH values of feed solutions. Fluxes of the blend membranes were larger at low pH values of feed solutions than that at high pH values. The pH-responsive ability of the mem-branes was enhanced with the increase of the degree of PMAA near-surface coverage.     

Kinetics and Mechanism of Copolymerization of α-terpineol with Methylmethacrylate in Presence of Azobisisobutyronitrile as an Initiator

The radical copolymerization of -terpineol with methyl-methacrylate in xylene at 80±0.1C for 50 minutes in the presence of azobisisobutyronitrile (AIBN) follows ideal kinetics and results in the formation of a functional and random copolymer. The activation energy is 33 KJ/mole. The IR spectrum and NMR spectra of the copolymer(s) shows the bands at 1750 and 3400 cm^–1 for ester group of methylmethacrylate and alcoholic group of -terpineol and peaks at 3 to 4 for methoxy group and at 6.5 to 7.5 due to alcoholic group of methylmethacrylate and -terpineol repectively. The values of reactivity ratios, calculated by Kelen–Tüdos method, are r ₁ (MMA) = 0.18 and r ₂ (-terpineol) = 0.046. The Alfrey-Price; Q–e parameters for -terpineol has been calculated as 0.149 and 2.486. The mechanism of copolymerization has been elucidated and it is concluded that the double bond present in the monocyclic ring of -terpineol is an active site for copolymerization and the alcoholic group of -terpineol remain to give functional copolymer.