Coionomeric mixtures of polyhydroxyethers and ethylene methacrylic acid copolymers. II. Compatibilizers for blends of polybutylene terephthalate and ethylene butyl acrylate copolymers

Blends of polybutylene terephthalate and ethylene butyl acrylate copolymers were studied at two extreme concentration levels so that each polymer would form, in turn, a particulate dispersed phase. The blends contained 5% by weight of a coionomeric compatibilizer, which was produced from 1 : 1 mixtures of a polyhydroxy ether of bisphenol A and the sodium ionomer of an ethylene methacrylic acid copolymer, using sodium ethoxide to enhance the formation of ionomeric clusters together with an A-B-A block oligomer to assist the solubilization of the two ionomeric polymers. In all cases the addition of the coionomeric compatibilizer mixture to the blend was found to decrease the size of the dispersed particles with a concomitant reduction in the interphase gap. It was also observed that the dispersed polymer exhibited a lower level of crystallinity and a slightly lower melting point than when it was present as a matrix, particularly for the case of the ethylene butylacrylate copolymer. The inability of the compatibilizer to completely prevent the formation of an interfacial gap which did not allow the blends to achieve more substantial improvements in mechanical properties, was attributed to the vast difference in crystallization temperature between the two polymers. © 1993 John Wiley & Sons, Inc.     

Synthesis, formulation and evaluation of novel zinc-calcium phosphate-based adhesive resin composite cement

Three novel adhesive oligomers having carboxylic acid and methacrylate groups were synthesized, characterized and used to formulate composite bone cements with newly synthesized zinc-calcium-silicate phosphate. The optimal formulation was determined based on types of oligomer, oligomer/diluent ratio, initiator concentration, and filler level using compressive strength (CS) and curing time (CT) as screening tools. Shrinkage, exotherm and aging of the formed composite cements were also evaluated. Results show that the experimental cement was 186% higher in CS, 16% higher in diametral tensile strength, similar in flexural strength, 56% less in exotherm and 64% less in shrinkage, as compared to conventional polymethylmethacrylate cement. The optimal concentrations for initiators were found to be 1.5% (by weight) for both benzoyl peroxide and N,N^′-dimethyl-p-toluidine. With increasing initiator concentration, diluent content and zinc oxide content in the cement formulation, CS of the cement increased but curing time decreased. Shrinkage and exotherm of the cement decreased with increasing filler level. CS was not proportional to an increase of filler level and CT increased with an increase of filler level. During aging, the cement showed an increase of strength over 24 h and then no change for over nine months. It appears that this novel cement may be a potential candidate for orthopedic restoration if its biological performance is good and the formulation is optimized.     

A Study of Photo- and Thermo-initiated Polymerised Dimethacrylates by Three Tthermal Analysis Techniques

Photo-initiated polymerisation of dimethacrylate oligomers provide an easy method for producing highly crosslinked polymer networks. The physical properties of the material are dependent on the polymerisation conversion value. The determination of this conversion value is quite difficult on the final product. The first step is to measure a characteristic temperature of the glass transition. The weakness of the DSC glass transition signal makes this measure unrealisable while the DMA tan peak is broad and weak. At the difference of these two thermal analysis techniques, TSDC gives an observable signal and a T_α temperature close to the glass transition temperature region. The bad sample preparation reproducibility observed was attributed to the high conversion rate. This revised version was published online in July 2006 with corrections to the Cover Date.     

Time-resolved fluorescence of α-(9-anthryl)-ω-(1-naphthyl)-oligosilanes: intramolecular electronic energy and charge transfer through π-π and σ-π interactions

The photophysical properties of a series of α,ω-diaryloligosilanes: (9-anthryl)-(SiMe₂)_n-(1-naphthyl) (1-4, and 6), n=1, 2, 3, 4, and 6, were investigated. For n?2, the intramolecular exciplex emission was observed in cyclohexane. For the stationary and the time-resolved fluorescence (TR-FL) measurements, the excitation of the naphthyl moiety showed a very efficient intramolecular energy transfer to the anthryl moiety, thus only fluorescence from the anthryl moiety was observed. In the case of 4 and 6, a charge-transfer (CT) emission was observed in acetonitrile. Then TR-FL of 6 revealed that the intramolecular-energy transfer from the naphthyl to anthryl moieties is faster than the CT.     

萜烯低聚物与马来酸酐的加成反应及其制备环氧树脂的研究

松节油经阳离子聚合反应可生成聚萜烯。其中分子量较大 ,软化点在 80℃以上部分称为萜烯树脂 ,广泛用作热熔胶、压敏胶的增粘剂。而分子量较小 ,常温下为液体的部分称萜烯低聚物 ,由于其软化点低 ,一般不适合作增粘剂使用。迄今为止 ,萜烯低聚物作为一种工业副产品 ,国内外尚未见有效的利用。目前 ,我国萜烯树脂年生产能力近 2 0 0 0 0吨 ,其中每年副产萜烯低聚物 30 0 0多吨 ,均用作燃料使用。如能将这部分产品进行化学改性 ,制备出适合于工业用途的精细化学品 ,将会大大提高其价值。萜烯低聚物的成分比较复杂 ,主要是三萜和二萜聚合物 ,其…     

Low molecular weight aromatic compounds possessing a nonflammable characteristic in fluoroalkyl end‐capped acrylic acid oligomer/silica nanocomposite matrices after calcination at 800 °C under atmospheric conditions

Fluoroalkyl end‐capped acrylic acid oligomer [R_F‐(ACA)_n‐R_F] reacted with tetraethoxysilane and silica nanoparticles in the presence of low molecular weight aromatic compounds [ Ar‐H ] such as cetylpyridinium chloride (CPC) and bisphenol AF under alkaline conditions to afford R_F‐(ACA)_n‐R_F/SiO₂ nanocomposites‐encapsulated Ar‐H in 47–94% isolated yields. These fluorinated silica nanocomposites‐encapsulated Ar‐H can exhibit no weight loss behavior corresponding to the contents of Ar‐H after calcination at 800 °C under atmospheric conditions, although fluoroalkyl end‐capped acrylic acid oligomer in the nanocomposites decomposed completely under similar conditions. UV‐vis spectra of well‐dispersed methanol solutions of R_F‐(ACA)_n‐R_F/SiO₂/CPC nanocomposites before calcination show that CPC can be encapsulated into fluorinated silica nanocomposites with encapsulated ratios: 23–43%. The fluorinated nanocomposites after calcination was found to exhibit a higher antibacterial activity related to the presence of CPC in the composites. Encapsulated bisphenol AF into R_F‐(ACA)_n‐R_F/SiO₂ nanocomposites before and after calcination at 800 °C can exhibit a good releasing ability toward methanol with released ratios: 48 and 26%, respectively. ¹H MAS NMR, HPLC analysis, and LC‐MS spectra of R_F‐(ACA)_n‐R_F/silica nanocomposites‐encapsulated bisphenol AF also showed the presence of bisphenol AF in the nanocomposites even after calcination at 800 °C under atmospheric conditions. These findings suggest that CPC and bisphenol AF can exhibit a nonflammable characteristic in the fluorinated silica nanocomposites. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Alignment of liquid crystal and dichroic dye molecules in mixed Langmuir and Langmuir-Blodgett films

A study of dichroic dye-liquid crystal mixtures (guest-host systems) in monolayers formed at a gas-liquid interface (Langmuir films) and at a solid surface (Langmuir-Blodgett films) has been made. As a host 4- n -octyl-4′-cyanobiphenyl (8CB) or 4- n -pentyl-4″-cyano- p -terphenyl (5CT) were chosen, while three dichroic azo dyes with various molecular structures were used as guest species. The dyes were added to the liquid crystal matrices at a concentration corresponding to the whole range of molar fractions and the surface pressure-mean molecular area isotherms for Langmuir films were recorded. On the basis of the isotherms, conclusions about the molecular organization and the miscibility of the components in the ultrathin films were drawn. The Langmuir films were transferred onto the quartz plates at surface pressures below the collapse point. The polarized absorption spectra of the Langmuir-Blodgett films were recorded and information about the alignment and intermolecular interactions in the mixtures of the non-amphiphilic dichroic dyes and the liquid crystals with strongly polar terminal groups were obtained.     

Synthesis and ring-opening copolymerization of cyclic aryl ester dimers

Two kinds of cyclic aryl ester dimers have been synthesized by reaction of phthaloyl dichloride with bisphenols via interfacial polycondensation. The cyclic dimers readily undergo anionic ring-opening polymerization or copolymerization in the melt by using sodium benzoate as the initiator, producing linear, high molecular weight polyesters. The contents of cyclic dimers in the homopolymers P1, P2, and copolymer P12 are 13.7%, 10.2%, 2.9%, respectively, which indicates that ring-opening copolymerization of cyclic dimers may impel the conversion of cyclic dimers and decrease the content of cyclic dimers in the resulting copolymer. Moreover, the isothermal chemorheology of the ring-opening copolymerization of cyclic dimers indicates that the reactivemoltenmixture has low shear viscosity and the viscosity increases slowly in the initial stage of ring-opening polymerization.     

pH‐Triggered Self‐Assembly of Cellulose Oligomers with Gelatin into a Double‐Network Hydrogel

Multicomponent systems for self‐assembled molecular gels provide huge opportunities to generate collective or new functions that are not inherent in individual single‐component gels. However, gelation tends to require careful and complicated procedures, because, among a myriad of kinetically trapped structures related to the degree of mixing of multiple components over a wide range of scales, from molecular level to macroscopic scale, a limited number of structures that exhibit the desired function need to be constructed. This study presents a simple method for the construction of double‐network (DN) hydrogels with improved stiffness composed of crystalline cellulose oligomers and gelatin. The pH‐triggered self‐assembly of cellulose oligomers leads to the formation of robust networks composed of crystalline nanofibers in the presence of dissolved gelatin, followed by cooling to allow for the formation of soft gelatin networks. The resultant DN hydrogels exhibit improved stiffness; the improvement in gel stiffness with double networking is comparable to that of previously reported DN hydrogels produced via a time‐consuming enzymatic reaction.