High-pressure synthesis and optical limiting property of cyclic diphenylacetylene oligomer

New conjugated oligomers were synthesized by reacting diphenylacetylene under high pressure of 0.13–0.76 GPa at 250 and 300°C for 1–10 h. The number-average molecular weight M _n, and the weight-average molecular weight M _w increased with pressure, but those values were independent of temperature and time (M _n, 320–490; M _w, 350–580). Elementary analysis, field desorption mass spectrometry, Fourier transform infrared, and ¹³C nuclear magnetic resonance experiments revealed that the oligomer above and including pentamer was a new compound having cyclic structure. Toluene solutions of the oligomer (400 M _n) contained within a quartz cell were irradiated with the pulse from a frequency-doubled Nd : Yag laser at 532 nm. The transmittance of the solution decreased with input fluence, and we observed an optical limiting property with saturated output fluence. As the concentration of the oligomer increased, the saturated output fluence decreased. The optical limiting property was analyzed according to the reverse saturable absorption mechanism. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:129–135, 1998     

Synthesis and thermoanalysis of emulsion terpolymers of N‐phenylmaleimide,styrene, and acrylonitrile

Terpolymers of N‐phenylmaleimide (PMI), styrene, and acrylonitrile (AN) were synthesized by emulsion polymerization. The thermal properties of terpolymers at different PMI and AN feed contents were investigated by differential scanning calorimetry, torsional braid analysis, thermogravimetric analysis, and a Vicat softening point test. The results showed the glass‐transition temperature and decomposition temperature of the terpolymers increased with increasing PMI feed content. Furthermore, the Vicat softening point of the terpolymers rose with PMI feed content. The weight‐ and number‐average molecular weights (M̄_w and M̄_n) of the terpolymers were also determined by gel permeation chromatography. The results showed that the M̄_w and M̄_n of the terpolymers decreased with increasing PMI feed content and increased with increasing AN feed content. The mechanical properties (tensile strength and impact strength) of the terpolymers decreased with increasing PMI feed content and increased with increasing AN feed content. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1067–1073, 2001     

Butyllithium-initiated anionic synthesis of well-defined poly(styrene-block-ethylene oxide) block copolymers with potassium salt additives

Poly(styrene-block-ethylene oxide) (PS–PEO) diblock copolymers have been synthesized with predictable block molecular weights and narrow molecular weight distributions. sec-Butyllithium-initiated polymerization of styrene was effected in benzene solution followed by ω-end-group functionalization with ethylene oxide to form the corresponding polymeric lithium alkoxide (PSOLi). Block copolymerization of ethylene oxide initiated by the unreactive PSOLi was promoted by addition of dimethylsulfoxide and either potassium t-butoxide, potassium t-amyloxide or potassium 2,6-di-t-butylphenoxide. Although the PS–PEO block copolymer product contained some poly(ethylene oxide) homopolymer, the poly(ethylene oxide) block M̄_n was in good agreement with the calculated value and the molecular weight distribution of the final block was generally narrow (M̄_w/M̄_n ≤ 1.1). The amount of PEO homopolymer was minimized using potassium 2,6-di-t-butylphenoxide rather than potassium t-alkoxides.     

Copolymerization of 4-chlorophenyl acrylate with methyl acrylate: synthesis,characterization, reactivity ratios,and their applications in the leather industry

4-Chlorophenyl acrylate (CPA) was prepared by reacting 4-chlorophenol and acryloyl chloride in the presence of triethylamine in ethyl acetate solution. Poly(4-chlorophenyl acrylate) and copoly(4-chlorophenyl acrylate–methyl acrylate) were synthesized by the free radical polymerization in ethyl acetate at 70°C. All the polymers were characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopic techniques. The composition of the copolymers was determined by the ¹H-NMR spectroscopic technique, that is, by integrating the aromatic peaks corresponding to the 4-chlorophenyl acrylate unit against the carbomethoxy group in the methyl acrylate unit. The reactivity ratios were calculated by Fineman–Ross, Kelen–Tudos (K–T), and the extended Kelen–Tudos methods. The values of r₁ and r₂ obtained by these methods were in close agreement with each other; that is, r₁(CPA) = 0.64 and r₂(MA) = 0.13 by the K–T method. The number-average molecular weight (M̄_n = 1.55 × 10³), the weight-average molecular weight (M̄_w = 8.39 × 10³), and the polydispersity index (M̄_w/M̄_n = 5.42) of poly(CPA) were determined by gel permeation chromatography (GPC). Thermal properties of the polymers were studied in a nitrogen atmosphere using thermogravimetric analysis (TGA). As the CPA increases in the copolymer, thermal stability of the copolymer increases (e.g., 90% weight loss occurs at 480°C for 20 mol % CPA, whereas the same weight loss occurs at 571°C for 80 mol % CPA). Acrylic binders, based on the CPA–MA–BA terpolymer, of different glass transition temperatures were prepared for applications in leather industry as top coat and base coat materials. These acrylic emulsions were cast into thin films, and their characteristics were tested for physical properties. These acrylic emulsions were applied as a base coat on leather, and the compositions having T_g values of 1.08 and 9.25°C were found to have excellent properties as base coats for leather when compared with commercial samples. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1153–1160, 1999     

Determination of glass transition temperature from dielectric analysis for a series of epoxide oligomers

Dielectric properties have been investigated for a bisphenol-A type epoxide oligomer, whose weight average molecular weight (M?_w) was 9454. The dielectric α-relaxation of the oligomer was found to be governed by the Havriliak–Negami equation as well as the same series of oligomers with smaller M?_ws (388≦M?_w ≦ 3903). The dielectric relaxation times (τ)s for the oligomers with different M?_ws (1396 ≦ M?_w ≦ 9454) can be expressed by the Williams–Landel–Ferry (WLF) equation as a function of the glass transition temperature (T_g) at fixed temperatures from 70 to 100°C. The finding indicates that the T_g of the epoxide oligomer is calculated from the τ through the WLF equation, providing the relation between T_g and τ. The same type of WLF equation was also successfully applied to describe the T_g, dependence of the practical dielectric relaxation time (τ_p), which was obtained from the peak of the dielectric loss vs. frequency curve. The τ_p can be calculated more easily than the τ, based on the Havriliak–Negami equation, not only in the measurement of epoxide oligomer, but also in that of the reactive epoxy resin systems during curing. The T_g of an epoxy–aromatic amine system, which was determined from the τ_p nondestructively detected in the dielectric cure monitoring, was consistent with the T_g experimentally measured by differential scanning calorimetry (DSC).     

Free volume and dipole mobility in an epoxide oligomer before crosslinking

The free volume of a bisphenol‐A‐type epoxide oligomer (DGEBA) was studied using Williams–Landel–Ferry parameters and thermal expansion coefficients above and below the glass transition temperature (T_g). The values of the free‐volume fraction at the T_g are around 0.02 for the DGEBA oligomers having weight‐average molecular weights (M _w's) from 1396 to 2640. The dipole mobility, which was obtained from the analysis of the temperature dependence of the dielectric relaxation time, was compared with the segment mobility in terms of the critical volume for the transport of each moving unit. The critical volume for the segment transport increases with increase of the M _w of the oligomer. The critical volume for the dipole movement, on the other hand, is not different between the oligomers studied (1396 ≤ M _w ≤ 2640), which leads to that the dipole mobility in the epoxide oligomer is smaller than is the segment mobility. The low mobility of the dipole is considered to result from the molecular interaction restricting the dipole movement, especially in a smaller M _w oligomer. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 207–214, 1999     

Relationship between melt viscosity and dielectric relaxation time for a series of epoxide oligomers

Melt viscosity has been investigated for a series of bisphenol-A type epoxide oligomers with different weight-average mol wts (M?_w), ranging from 388 to 2640. The temperature dependence of the melt viscosity is described by the Williams–Landel–Ferry (WLF) equation. The melt viscosity η is correlated with both the direct current (dc) conductivity σ and the dielectric relaxation time τ. The two relationships between these three properties, σ·η^κ = const (0.63 ≦ κ ≦ 1.12) and η/τ^? = const (0.73 ≦ ? ≦ 1.06), are experimentally derived. Both exponents, κ and ?, depend on the M?_w of the oligomer. The lower M?_w oligomer has the larger value of κ. The κ value is close to unity for the low M?_w oligomer, which agrees with Walden's rule, σ·.η = const, applicable to most low mol wt liquids. The ? value is near unity for the epoxide oligomer with higher M?_w than 2000, which means that the melt viscosity is proportional to the dielectric relaxation time. The low M?_w oligomer (M?_w < 2000), on the other hand, has a smaller value of ? below unity. The result indicates that the melt viscosity is not proportional to the dielectric relaxation time for the low M?_w epoxide oligomer, whose dielectric α-relaxation is not governed by the Debye equation. © 1993 John Wiley & Sons, Inc.     

Preparation and applications of novel fluoroalkyl end‐capped sulfonic acid oligomers–silica gel polymer hybrids

Fluoroalkyl end‐capped 2‐methacryloxyethanesulfonic acid homo‐oligomer [R_F–(MES)_n–R_F] and 2‐methacryloxyethanesulfonic acid–N,N‐dimethylacrylamide co‐oligomers [R_F–(MES)_x–(DMAA)_y–R_F] reacted with tetraethoxysilane (TEOS) under acidic conditions to afford R_F–(MES)_n–R_F homo‐oligomer–SiO₂ polymer hybrid and R_F–(MES)_x–(DMAA)_y–R_F co‐oligomer–SiO₂ polymer hybrid, respectively. Thermogravimetric–mass spectra showed that the thermal stability of R_F–(MES)_n–R_F homo‐oligomer–SiO₂ polymer hybrid was superior to that of traditionally well‐known perfluorinated ion exchange polymers such as Nafion 112 (TR). The sol solutions of the fluorinated co‐oligomer–SiO₂ polymer hybrid were applied to the surface modification of glass to exhibit not only a strong oleophobicity imparted by fluorine but also a good hydrophilicity on the glass surface. On the other hand, R_F–(MES)_x–(DMAA)_y–R_F co‐oligomer reacted with TEOS in the presence of a variety of silica nanoparticles (mean diameters: 11–95 nm) under alkaline conditions to afford fluoroalkyl end‐capped oligomers–silica nanoparticles (mean diameters: 32–173 nm) with a good dispersibility and stability in methanol. Similarly, a variety of fluorinated oligomers containing sulfo groups–silica nanoparticles were prepared by the homo‐ and co‐oligomerizations of fluoroalkanoyl peroxides with 2‐methacryloxyethane sulfonic acid (MES) and comonomers such as N,N‐dimethylacrylamide (DMAA) and acryloylmorpholine (ACMO) in the presence of silica nanoparticles. Interestingly, these isolated fluorinated particle powders were found to afford nanometer size‐controlled colloidal particles with a good redispersibility and stability in aqueous and organic media such as methanol. These fluorinated nanoparticles containing sulfo groups were also applied to an excellent heterogeneous catalyst for Bronsted acid‐catalyzed transformations. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 110–117, 2007     

Cellulose degradation in xanthate process

Changes in degree of polymerization (DP) of cellulose during the viscose process were investigated by determining the number average molecular weight (M̄_n), weight average molecular weight (M̄_ω), and polydispersity (M̄_ω/M̄_n) giving molecular weight distribution (MWD). In general, a reduction in DP from the pulp stage to the final filament stage was noticed. Maximum degradation was observed to take place during xanthation and not during aging as sometimes claimed. Among the four methods used for gel permeation chromatography (GPC), Universal calibration HDV method, not involving viscosity measurement, gave the best and most reproducible values.     

Thermal properties and biodegradability of the copolymers of l-lactide, ?-caprolactone, and ethylene glycol oligomer with maleate units and their crosslinked products

Copolymers of l-lactide (LLA), ?-caprolactone (CL), and ethylene glycol oligomer (EGO) were synthesized by ring-opening copolymerization of CL and LLA initiated by EGO at the LLA/CL molar ratios of 7/3, 5/5, and 3/7. The resulting viscous ternary copolymers (PLCE) with weight average molecular weight (M_w) ca. 3000 were reacted with maleic anhydride to give unsaturated group-containing copolymer (PLCEM) with M_w 6000-8000. The degree of unsaturation of PLCEM was 0.3-0.6 per one EGO block. The PLCEM was cured with benzoyl peroxide (BPO) to give a viscoelastic soft material insoluble in any solvent. The DSC analysis of the copolymers revealed that all the copolymers are amorphous materials having a glass transition temperature (T_g), which increased with increasing LLA/CL ratio. The crosslinked PLCEM showed a higher T_g than the corresponding PLCE and PLCEM. The crosslinked PLCEM showed good biodegradability, when measured by a BOD method using activated sludge.     

Influence of Aluminium Alkyl Compounds on the High‐Pressure Polymerization of Ethylene with Ternary Metallocene‐Based Catalysts. Investigation of Chain Transfer to the Aluminium

The influence of aluminium alkyl compounds on metallocene‐catalyzed high pressure polymerizations of ethylene has been investigated at 150 MPa and 180°C in a continuously operated autoclave. The catalysts were based on the metallocenes bis(cyclopentadienyl)zirconium dichloride (Cp₂ZrCl₂) and diphenylmethylene (cyclopentadienylfluorenyl)zirconium dichloride (Ph₂C‐(CpFlu)ZrCl₂), which were preactivated outside the reactor with triisobutylaluminium (TiBA) and N,N‐dimethylanilinium tetrakis(pentafluorophenyl)borate (DMAP, [PhNHMe₂][B(C₆F₅)₄]). The concentrations of triisobutylaluminium (TiBA) and triethylaluminium (TEA) in the reactor were varied over a wide range, using a separate dosing for these two aluminium alkyl compounds. Productivity and polymer properties strongly depended on the type and the concentration of the aluminium alkyl compound used. Highest productivities and molecular weights were obtained with low concentrations of TiBA in the reactor. Up to a concentration of 30 molppm Al in the reactor, unimodal polymers were formed with M̄_w/M̄_n between 2 and 3. With higher aluminium concentrations the products formed contained small amounts of waxes, due to oligomerization catalyzed by the aluminium alkyl compounds. The molecular weight distributions (MWDs) of these products could be described as a superimposition of two Schulz‐Zimm distributions. All MWDs were analyzed with regard to the amount of waxes produced by ethylene oligomerization and with regard to the influence of chain transfer reactions to the aluminium. The rate constants of chain transfer to aluminium, in relation to the rate constants of insertion of ethylene, were estimated.     

Synthesis of oligo‐ortho‐azomethinephenol and its oligomer–metal complexes: Characterization and application as anti‐microbial agents

The oxidative polycondensation reaction conditions and optimum parameters of o‐phenylazomethinephenol (PAP) with oxygen (air) and NaOCl were determined in an aqueous alkaline solution at 60–98°C. The properties of oligo‐o‐phenylazomethinephenol (OPAP) were studied by chemical and spectra analyses. PAP was converted to dimers and trimers (25–60%) by oxidation in an aqueous alkaline medium. The number average molecular weight (M_n), mass average molecular weight (M_w), and polydispersity index (PDI) values were 1180 g mol^?1, 1930 g mol^?1, and 1.64, respectively. According to these values, 20–33% of PAP turned into OPAP. During the polycondensation reaction, a part of the azomethine (? CH?N? ) groups oxidized to carboxylic (? COOH) group. Thus, a water‐soluble fraction of OPAP was incorporated in the carboxylic (? COOH); (2–20%) group. Also, the structure and properties of oligomer–metal complexes of OPAP with Cu(II), Ni(II), Zn(II), and Co(II) were studied. Antimicrobial activites of the oligomer and its oligomer–metal complexes were tested against B. cereus, L. monocytogenes, B. megaterium, B. subtilis, E. coli, Str. thermophilus, M. smegmatis, B. brevis, E. aeroginesa, P. vulgaris, M. luteus, S. aureus, and B. jeoreseens. Also, according to differential thermal analysis and thermogravimetric analysis, OPAP and its oligomer–metal complexes were stable throughout to temperature and thermo‐oxidative decomposition. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2004–2013, 2002     

Theoretical pressure dependency of carbon dioxide solubility under hydrate–liquid water equilibrium

The effect of pressure on carbon dioxide solubility in water is significantly smaller than that of temperature under hydrate–liquid water (H–L_w) equilibrium. As a result, experimental values of carbon dioxide solubility in the water rich liquid phase under H–L_w equilibrium are often inconclusive and in some cases contradictory. This work proposes a theoretical derivation, based on fundamental thermodynamics, of the gas hydrate former solubility dependency on pressure for any binary system under two‐phase equilibrium. The obtained expression is applied to the carbon dioxide–water system under both hydrate–liquid water and vapour–liquid water equilibrium. It is shown that the solubility of carbon dioxide in the water rich liquid phase increases with increasing pressure under H–L_w equilibrium. The predicted trend is then compared to the limited experimental data available in the literature.     

Poly(pent‐1‐ene) Synthesized with the Syndiospecific Catalyst i‐Pr(Cp)(9‐Flu)ZrCl2/MAO

1‐Pentene was polymerized with the syndiospecific catalyst system i‐PrC(Cp)(9‐fluorenyl)ZrCl₂/MAO. The molar mass of the resulting polymers depends strongly on the reaction temperature and decreases from M̄_w = 126 000 at 0°C to M̄_w = 46 000 at 100°C, but is more or less independent of the monomer and the MAO concentration. The influence of reaction temperature and concentrations of MAO and monomer on the type of end‐groups generated during the chain termination, as well as on the type of stereoerror, was investigated. The degree of tacticity was dependent on the polymerization temperature with [rrrr] > 0.99 at 0°C and [rrrr] = 0.75 at 100°C.     

Chemical Modification of Methanol-Insoluble Kraft Lignin Using Oxypropylation Under Mild Conditions for the Preparation of Bio-Polyester

Methanol-insoluble high-molecular weight (M_w = 26,610 g mol^?1) soft wood kraft lignin was oxypropylated under the mild condition of 40°C and 1 atm for 12 h in the presence of NaOH catalyst for the production of bio-polyester. Fourier transform infrared spectra showed that polyether chains were extended due to the oxypropylation reaction. The M_w and M_n of the oxypropylated lignin were 46,330 and 17,110 g mol^?1, respectively. The high-molecular weight oxypropylated lignin was reacted with sebacic acid or polybutadiene (dicarboxy terminated) for bio-polyester synthesis. While the decomposition temperatures of the oxypropylated lignin were 217°C and 367°C, those of the bio-polyesters prepared with sebacic acid and polybutadiene (dicarboxy terminated) were 380°C and 453°C, respectively, indicating that the bio-polyesters possessed enhanced thermal properties. The oxypropylation of methanol-insoluble high-molecular weight lignin under mild conditions is one of the promising approaches for preparing bio-plastics with an enhanced thermal property.     

Synthesis of high molecular weight poly(L‐lactic acid) via melt/solid polycondensation: Intensification of dehydration and oligomerization during melt polycondensation

Melt/solid state polycondensation (MP/SSP) is a cost‐effective route for synthesis of high molecular weight poly(L ‐lactic acid) (PLLA). However, the reaction rates in its four stages need to be enhanced greatly and the reaction times to be shortened largely before the MP/SSP technology can be industrialized. In this study, a new catalyst addition policy, i.e., adding TSA at the dehydration stage and SnCl₂·2H₂O at the MP stage, and more appropriate temperature and pressure programs were presented and applied in the MP process of LLA. The presence of TSA from dehydration appeared very effective for speeding up the dehydration and oligomerization stages as well as depressing racemization in the whole MP process. The polymerization degree (X_n) of oligomer was clearly increased, and the reaction time was shortened to a great extent. Direct using reduced pressure was also very helpful for intensifying the dehydration stage, only leading to LLA loss as little as 2%. A PLLA with M_w of 44,000 and optical purity of 96.8% suitable for subsequent SSP was produced after dehydration for 2 h, oligomerization for 2 h and MP for 4 h under appropriate conditions. And an interesting strong dependence of the M_w of final PLLA product on the X_n of the oligomer was observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Shear degradation of polyisobutene

A polyisobutene of M?_w 1.98 × 10⁶, M?_w/M?_n 1.8, was extruded in an Instron capillary rheometer. Shear degradation occurred at high shear stresses, approaching melt fracture, and was more prominent at lower extrusion temperatures for tests at 60–140°C. The capillary was 2.0 in. long with a length/diameter ratio of 66.7 and a 90° entrance angle. Repetitive extrusions at constant shear rate caused a decrease in a molecular weight and a simultaneous narrowing of the molecular weight distribution. Extrudate expansion was measured after each successive capillary pass for tests at 80°C. Extrudate swelling correlated well with (M?_z+1) M?_z/M?_w, except for the two first passes, where melt fracture was pronounced. The correlation with equilibrium extrudate expansion was almost as good for (M?_z/M?_w)^3.7 (Mill's correlation) and for M?_z+1 alone. The efficiency of bond rupture is low, with the energy required to rupture 1 mole of bonds being about 200,000 kcal at 80°C.     

Hydrolysis of 1,4-cyclohexanedimethanol-based copolyester

The solid state hydrolysis of a copolyester based on a mixture of 1,4-cyclohexanedimethanol and ethylene glycol condensed with terephthalic acid was studied at 100°C and 57 to 96 kPa water vapor partial pressure (55% to 95% relative humidity). The equilibrium water sorption in weight percent (C_∞) was found to be where P is the water vapor partial pressure in kPa. For specimens 0.32-cm thick, it took about 24 h to reach 0.9C_∞. The intrinsic viscosity (IV) was measured and used to calculate the relative change in molecular weight (M?_w) from the relationship IV ∝? (M?_w)^0.7. The decrease in molecular weight was linear with time, and the rate of decrease was found to be proportional to C_∞; the empirical correlation is where the rate constant, k, is in day^?1. A decrease of 50% in M?_w was observed after 22 days at 95% relative humidity.     

The preparation of multiaxially oriented polyethylene morphologies with high mechanical properties in planar direactions

The development of multiaxially oriented films of low molecular weight (M_w ≈ 59,000) high density polyethylene with high mechanical properties in planer directions has been pursued by inducing fibrillar crystallization under curvilinear flow conditions in a contained geometry using an extrudomolding process and by simulating similar crystallization conditions in an optical plate–plate rheometer. The films, like the uniaxially drawn morphologies of the same low molecular weight high density polyethylene by solid-state extrusion, had a high modulus (12–20 GPa) and strength (0.25 GPa) along the residual flow lines but they exhibited also a modulus enhancement (5 GPa) in the transverse direction as a result of the orientation gradient of the molecular chains in the thickness directions.     

Combined effect of temperature and thickness on work of fracture parameters of unplasticized PVC film

The combined effect of temperature and thickness on the essential work of fracture (EWF) parameters for an unplasticized poly(vinyl chloride) (uPVC) film was investigated using double edge notched tension specimens. It was found that for the range of temperatures (23°C to 60°C) and thicknesses (0.15 mm to 0.40 mm) studied here, specific essential work of fracture (w_e) was independent of temperature at each thickness but increased with thickness at each temperature. It was found that at each temperature, w_e and its yielding (w_e,y) and necking/tearing components (w_e,nt), all increased linearly with increasing thickness. However, whilet w_e showed no significant variation with respect to temperature, its yielding component (w_e,y) decreased and its necking/tearing component increased (w_e,nt) with increasing temperature. It was found that estimated values of w_e and its components w_e,y and w_e,nt via crack opening displacement values were by and large unsatisfactory, being either much higher or lower than the directly measured values.