Molecular weight and arm number of a star‐shaped styrene–butadiene block copolymer synthesized on a pilot‐vessel scale

To improve the rheological properties and processability of industrial rubbers, star‐shaped styrene–butadiene–styrene (SBS) block copolymers were synthesized and characterized in this work. Through the variation of the ratio of divinylbenzene to the diblock anion, a series of SBS samples with three to six arms were prepared. Multi‐angle laser light scattering (MALLS) and size exclusion chromatography (SEC) combined with light scattering (LS) were used to determine the weight‐average molecular weight (M_w), radius of gyration (〈S²〉^1/2), arm number, and chain conformation. The results from MALLS indicated that the M_w values of the star‐shaped SBS copolymers were 9.0, 13.0, 14.9, and 18.1 × 10⁴, which corresponded to three, four, five, and six arms, respectively. There was a lot of M_w and 〈S²〉^1/2 data for the many fractions in the SEC chromatograms of the SBS copolymers in tetrahydrofuran (THF) detected by LS, so the exponent of 〈S²〉^1/2 = KM_w^α was determined to range from 0.59 to 0.30 for the samples having three to six arms. An analysis of the results revealed that the star SBS copolymers existed in a sphere conformation in THF, and their chain density increased with an increase in the arm number. The viscosity of the six‐arm SBS copolymer was reduced significantly, compared with that of the SBS samples having three to five arms, when their M_w values were similar. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1853–1859, 2007     

Molecular architectures of four‐arm star‐shaped styrene‐butadiene copolymer

To understand the molecular architectures of styrene‐butadiene four‐arm star (SBS) copolymers, a size exclusion chromatography combined with laser light scattering (SEC‐LLS) has been used to determine their weight‐average molecular weight (M_w) and radius of gyration (〈S²〉^1/2), and a new method for the establishment of the Mark‐Houwink equation from one sample has been developed. Based on the Flory viscosity theory, we successfully have reduced the 〈S²〉^1/2 values of numberless fractions estimated from many experimental points in the SEC chromatogram to intrinsic viscosities ([η]). For the first time, the dependences of 〈S²〉^1/2 and [η] on M_w for the four‐arm star SBS in tetrahydrofuran at 25°C were found, respectively, to be 〈S²〉^1/2 = 2.62 × 10^?2 M (nm) and [η] = 3.68 × 10^?2 M (mL/g) in the M_w range from 1.4 × 10⁵ to 3.0 × 10⁵. From data of [η] and 〈S²〉^1/2 for linear and star SBS, we have obtained the information about the branching, namely, the ratios (g and g′) of 〈S²〉 and [η] for star SBS to that of the linear SBS of the same molecular weight, which agree with theoretical predictions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 961–965, 2005     

Statistics of star-shaped molecules III. Stars with branched nuclei

Number and weight average molecular weights and scattering behaviour of star molecules with extended branched nuclei are calculated by application of cascade theory. The nuclei considered arise from random polycondensation of monomers of the A₃ or of the A—B/C type. Nuclei of the first type are characterised by very large molecular polydispersities (M_w/M_n α M_w), while nuclei of the second type have less broad molecular weight distributions (M_w/M_n α M_n). The rays of the stars are assumed to be either monodisperse or to obey the Schulz—Flory “most probable” length distribution. Analytic expressions are given for M_w, M_n, 〈S²〉_z and the particle scattering factor P_z(h) which was averaged over the ensemble. The results are compared with stars of spherical and uniform nuclei whose molecular weights and mean square radii of gyration equal M_wN and 〈S²〉_zN from the other two types of nuclei. In the limit of very large ray lengths the scattering behaviour is determined solely by the number of branches z. At shorter chain length of the rays structure and polydispersity of the nuclei have marked influence. This influence is still easily noticed from the angular dependence of scattered light at chain lengths where no differences in the 〈S²〉_z versus M_w plot are detectable. The mean square radius of gyration depends only weakly on the number of rays and eventually becomes independent of it if z 15. In that limit 〈S²〉_z depends virtually on the length of the rays alone and its distribution. Stars whose rays have a most probable length distribution exhibit 〈S²〉_z values twice as large as stars with monodisperse rays. A procedure is suggested and discussed for the determination of the number and length of the rays if the scattering behaviour of the isolated nucleus and the isolated linear chains is known.     

Urea/NaOH aqueous solution as new solvent of aeromonas gum

Aeromonas (A) gum, an acidic heteropolysaccharide, formed aggregates easily in NaCl aqueous solution. A novel solvent of the A gum, which can prevent aggregation, was found to be 0.20M urea/0.25M NaOH aqueous solution. The weight‐average molecular weight (M_w), radius of gyration (〈s²〉^1/2), and intrinsic viscosity ([η]) of the samples were determined in 0.20M urea/0.25M NaOH aqueous solution at 25°C by light scattering (M_w, 〈s²〉^1/2) and viscometry ([η]). The values of M_w, 〈s²〉^1/2, and [η] were close to those in 0.20M lithium chloride/dimethylsulfoxide, in which the A gum exists as a semiflexible single chain, implying the same conformation for the A gum in 0.20M urea/0.25M NaOH aqueous solution. The results revealed that 0.20M urea/0.25M NaOH aqueous solution is a good solvent, which effectively avoids the aggregates of the A gum in aqueous solution. Moreover, it can be used to investigate the solution properties and chain conformation of water‐insoluble polysaccharides or the polysaccharides that are easily aggregated in aqueous systems. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1710–1713, 2005     

Properties of aqueous salt solutions of poly(vinylpyrrolidone). II. Polymer dimensions and thermodynamic quantities

The unperturbed dimensions and thermodynamic parameters of poly(vinylpyrrolidone) (PVP) have been studied in aqueous salt solutions, e.g. phosphates, mono- and dihydrogen phosphates, carbonates, sulphates of sodium and potassium. Values of K₀ ( = [η]_ΘM^-1/2, where [η]_Θ is intrinsic viscosity at the theta temperature and M is molecular weight) with M_w = 78 000 g mol^-1 were found to range from 4·63×10^-4 to 5·56×10^-4 dl g^-1, and root-mean-square end-to-end distances, 〈r²〉₀^1/2, ranging from 1·61×10^-6 to 1·68×10^-6cm were evaluated. Values of the characteristic ratio, C_n, the steric parameter, σ, and the enthalpy and the entropy of dilution parameters, χ_H and χ_S, have also been calculated, and the interaction parameter was found to be χ-0·5<-0·001 for aqueous salt solutions of PVP. ©1997 SCI     

Preparation of high‐molecular‐weight poly(L‐lactic acid)‐based polymers through direct condensation polymerization in bulk state

Poly(L ‐lactic acid‐co‐succinic acid‐co‐1,4‐butanediol) (PLASB) was synthesized by a direct condensation copolymerization of L ‐lactic acid, succinic acid (SA), and 1,4‐butanediol (BD) in bulk state using titanium(IV) butoxide (TNBT) as a catalyst. Weight average molecular weight (M_w) of PLASB increased from 3.5 × 10⁴ to 2.1 × 10⁵ as the content of SA and BD went up from 0.01 to 0.5 mol/100 mol of L ‐lactic acid (LA). PLASB having M_w in the range from 1.8 × 10⁵ to 2.1 × 10⁵ showed tensile properties comparable to those of commercially available poly(L ‐lactic acid) (PLLA). In sharp contrast, homopolymerization of LA in bulk state produced PLLA with M_w as low as 4.1 × 10⁴, and it was too brittle to prepare specimens for the tensile tests. M_w of PLASB synthesized by using titanium(IV)‐2‐ethyl(hexoxide), indium acetate, indium hydroxide, antimony acetate, antimony trioxide, dibutyl tin oxide, and stannous‐2‐ethyl 1‐hexanoate was compared with that of PLASB obtained by TNBT. Ethylene glycol oligomers with different chain length were added to LA/SA in place of BD to investigate effect of chain length of ethylene glycol oligomers on the M_w of the resulting copolymers. Biodegradability of PLASB was analyzed by using the modified Sturm test. Toxicity of PLASB was evaluated by counting viable cell number of mouse fibroblast cells that had been in contact with PLASB discs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 466–472, 2006     

Free radical scavenging activity of cellulase‐treated chitosan

Partially N‐acetylated chitosan was hydrolyzed by the cheap, commercially available, and efficient cellulase. The products, with different molecular weight, were comparatively investigated by GPC, FT‐IR, XRD, and NMR. The results show that the decrease of molecular weight led to transformation of crystal structure and increase of water‐solubility, but the chemical structures of residues were not modified. Superoxide anion radical and hydroxyl radical quenching assay were used for the evaluation of free radical scavenging activity of cellulase‐treated chitosan in vitro. Low molecular weight chitosan (LMWC3, M_w 1.7 × 10³) exhibited high scavenging activity against free radical. It scavenged 79.3% superoxide radical at 0.1 mg mL^?1. At 2.0 mg mL^?1, scavenging percentage of initial chitiosan, LMWC1 (M_w 27.3 × 10³), LMWC2 (M_w 5.9 × 10³), and LMWC3 (M_w 1.7 × 10³) against hydroxyl radical was 14.3%, 33.1%, 47.4%, and 65.9%, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and properties of polyurethane/benzyl amylose semi‐interpenetrating networks

A series of semi‐interpenetrating polymer networks (semi‐IPNs) films were prepared from 20 wt % of benzyl amylose (BA) of different M_w and castor oil‐based polyurethane (PU) in N,N‐dimethylformamide (DMF). The weight‐average molecular weight (M_w), and radii of gyration (<S²>_z^1/2) of benzyl amylose were determined by laser scattering measurement, and the results suggested BA was in a compact coil conformation in DMF. Furthermore, the properties and miscibility of the polyurethane/benzyl amylose (PUBA) films were studied by scanning electronic microscopy, differential scanning calorimetry, dynamic mechanical thermal analysis, ultraviolet–visible spectrophotometer, and tensile testing. The PUBA films possessed much higher optical transmittance and tensile strength than the pure PU film regardless of the molecular weight of BA, but lower values of elongation at break were observed. With decreasing of the BA M_w from 9.24 × 10⁵ to 2.69 × 10⁵, interestingly, the elongation at break of the films increased from 135 to 326%. This might be ascribed to the decrease of crosslinking density of PU networks and the enhancement in freedom of the molecular motion. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

An amphoteric water‐soluble copolymer. II. Effect of its molecular weight on the dispersion of barium titanate in water

An amphoteric water‐soluble copolymer, that is, polyacrylamide/(α‐N,N‐dimethyl‐N‐acryloyloxyethyl)ammonium ethanate (PAAM/DAAE) was synthesized and it showed the ability to disperse BaTiO₃ (BT) particles in aqueous solutions. In this work, the effect of molecular weight of this polymer on the dispersing properties was further examined. The results indicate that the effectiveness of three polymer samples with different molecular weights in the dispersion of BT particles is P2 (M_w = 1.1 × 10⁵) > P1 (M_w = 1.2 × 10⁴) > P3 (M_w = 3.0 × 10⁵). Apparently, P2 is most effective in dispersing the particles, reducing the viscosity of the suspensions, and obtaining highest green and sintered densities. This is attributed to the highest adsorption of this polymer onto BT powder, and causes strongest electrostatic and steric repulsions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 886–891, 2006     

Anionic polymerization of secondary aminostyrene and characterization of the polymer

Preparation by anionic living technique and characterization of poly(secondary aminostyrene) having narrow molecular weight distribution were investigated. N‐isopropyl‐N‐trimethylsilyl‐4‐vinylbenzylamine (SBA) was purified by use of sec‐butylmagnesium bromide as a purging reagent under high vacuum. SBA was anionically polymerized with n‐butyllithium or cumylpotassium in tetrahydrofuran at −78°C under high vacuum to yield the corresponding polymer (PSBA) in 100% yield. Subsequent deprotection of the trimethylsilyl group from PSBA produced poly(N‐isopropyl‐4‐vinylbenzylamine) (PBA) of the desired molecular weights (M_n: 1.3 × 10⁴–17 × 10⁴, determined by membrane osmometry) with narrow molecular weight distribution (M_w/M_n: 1.07–1.03, determined by gel permeation chromatography). The living lithium carbanion of PSBA can initiate styrene (St) to yield PSBA‐b‐PSt block copolymer (M_n = 4.0 × 10⁴, M_w/M_n = 1.05), and the polystyryllithium can initiate SBA to yield PSt‐b‐PSBA (M_n = 3.7 × 10⁴, M_w/M_n = 1.25). The deprotection of the trimethylsilyl group from the two block copolymers produced new block copolymers containing poly(secondary aminostyrene) block. Anionic reactivity of SBA and basic properties of PSBA are discussed in terms of the ¹³C chemical shift of β‐carbon in the vinyl group of SBA and steric effect. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2039–2048, 1999     

Silylated poly(4-hydroxystyrene)s as negative electron beam resists

Silylated poly(4-hydroxystyrene)s and radical polymerized 4-tert-butyldimethylsilyloxystyrene (TBDMSOSt) were examined as electron beam resists. Commercial poly(4-hydroxystyrene) (PHS) with M_w = 1.69 × 10⁴ and M_w/M_n = 5.41 was silylated with 1-(trimethylsilyl)imidazole and tert-butylchlorodimethylsilane. Both silylation reactions proceeded quantitatively to afford trimethylsilylated PHS with M_w = 3.93 × 10⁴ and M_w/M_n = 4.91, and tert-butyldimethylsilylated PHS with M_w = 4.08 × 10⁴ and M_w/M_n = 3.81. These 2 silyl ether polymers acted as a negative working resist to electron beam (EB) exposure. Sensitivity and contrast of tert- butyldimethylsilylated PHS were not affected by prebake temperature around its T_g of 97°C, while those of PHS were dependent on prebake temperature around its T_g of 160°C. At a prebake temperature of 125°C, the sensitivity parameter and the contrast γ value were obtained as follows: 3.93 × 10⁻⁴ C cm⁻² and 0.91 for PHS; 1.49 × 10⁻⁴ C cm⁻² and 1.06 for trimethylsilylated PHS; 1.84 × 10⁻⁴ C cm⁻² and 1.44 for tert-butyldimethylsilylated PHS. The silylation procedures obviously improved the sensitivity of PHS. TBDMSOSt was polymerized in bulk at 60°C with 2,2′-azobisisobutyronitrile (AIBN) as an initiator. The resultant poly(TBDMSOSt) possessed M_w = 3.01 × 10⁵ and M_w/M_n = 1.92 and exhibited a sensitivity of 1.60 × 10⁻⁵ C cm⁻² and a γ value of 1.47. More than 10 times enhancement of sensitivity was observed compared with tert-butyldimethylsilylated PHS. Such a high sensitivity is probably due to the high molecular weight of the bulk polymerized material. Poly(TBDMSOSt) resolved an isolated line of 0.20 μm width and 0.5 μm line and space patterns. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1151–1157, 1998     

Laser light-scattering studies of soluble high performance fluorine-containing polyimides

Two sets of soluble high performance polyimides synthesized from 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 2,2′-(trifluoromethyl)-4,4′-diaminobiphenyl diamine (PFMB), and from 2,2′-bis(trifluoromethyl)-4,4′,5,5′-biphenyl-tetracarboxylic dianhydride (HFBPDA) and 2,2′-(trifluoromethyl)-4,4′-diaminobiphenyl diamine (PFMB) have been investigated by static and dynamic laser light scattering (LLS) in tetrahydrofuran (THF) at 30°C. The calibrations, for 6FDA-PFMB: <R_g> (nm) = 3.87 × 10^?2 <M_w> ^0.568, <R_h> (nm) = 2.38 × 10^?2 <M_w>^0.560 and <D> (cm²/s) = 2.13 × 10^?4 <M_w>^?0.560; for HFBPDA-PFMB: <R_g> (nm) = 2.24 × 10^?2 <M_w>^0.626, <R_h> (nm) = 1.27 × 10^?2 <M_w>^0.621 and <D> (cm²/s) = 3.99 × 10^?4 <M_w>^?0.621, have been established, where <M₂>, <R_g>, <R_h> and <D> are the weight-average molar mass, the root mean square z-average radius of gyration, the z-average hydrodynamic radius and the z-average translational diffusion coefficient, respectively. A combination of <M_w> and the translational diffusion coefficient distribution G(D) leads to the calibrations of D (cm²/s) = 2.41 × 10^?4M^?0.564 and D (cm²/s) = 6.16 × 10^?4M^?0.656 for 6FDA-PFMB and HFBPDA-PFMB, respectively, where D and M correspond to monodisperse species. With these calibrations, we can convert a translational diffusion coefficient distribution G(D) into a corresponding molar mass distribution f_w(M). On the basis of the Kratky-Porod wormlike chain model, the persistence lengths (q) were found to be ? 3.3 nm and ? 4.5 nm, respectively, for 6FDA-PFMB and HFBPDA-PFMB, which indicates that both polyimide chains have an extended conformation. In addition, <R_g> / <R_h> ? (1.7-1.9) shows that they are in coil conformation. Therefore, we conclude that both polyimides have an extended coil conformation.     

Synthesis of star‐shaped poly(ϵ‐caprolactone) by samarium‐based tetrafunctional initiator and its dilute‐solution properties

An in situ–generated tetrafunctional samarium enolate from the reduction of 1,1,1,1‐tetra(2‐bromoisobutyryloxymethyl)methane with divalent samarium complexes [Sm(PPh₂)₂ and SmI₂] in tetrahydrofuran has proven to initiate the ring‐opening polymerization of ?‐caprolactone (CL) giving star‐shaped aliphatic polyesters. The polymerization proceeded with quantitative conversions at room temperature in 2 h and exhibited good controllability of the molecular weight of polymer. The resulting four‐armed poly(?‐caprolactone) (PCL) was fractionated, and the dilute‐solution properties of the fractions were studied in tetrahydrofuran and toluene at 30°C. The Mark–Houwink relations for these solvents were [η] = 2.73 × 10^?2M_w^0.74 and [η] = 1.97 × 10^?2M_w^0.75, respectively. In addition, the unperturbed dimensions of the star‐shaped PCL systems were also evaluated, and a significant solvent effect was observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 175–182, 2006     

Small-angle X-ray scattering from sodium hyaluronate in aqueous sodium chloride

Summary Four narrow-distribution samples of sodium hyaluronate with weight-average molecular weights M _w of 3.8 × 10³ to 1.1 × 10⁴ in 0.02 and 0.1 M aqueous NaCl at 25°C have been studied by small-angle X-ray scattering. Data for their z-average radii of gyration <S²>_z ^1/2 and particle scattering functions P(θ), together with previous <S²>_z data from light scattering for high molecular weights, are compared with relevant theories for the wormlike chain with or without excluded volume, using the parameters estimated previously from intrinsic viscosity ([η]) data. It is shown that for M _w lower than 1.1 × 10⁴, <S²>_z, P(θ), and [η] of the polysaccharide in the aqueous salts are all consistently explained by this model without excluded volume. Received: 8 December 1997/Accepted: 26 December 1997     

Study on conformational transition phenomena of poly(methyl methacrylate) in acetonitrile near theta conditions

The coil–globule transition for poly(methyl methacrylate) (PMMA) has been studied in a theta solvent, acetonitrile (Θ = 45 °C). The viscosity of PMMA was measured as a function of temperature in the range 26–55 °C. The contraction and expansion of the molecular chains are determined using the measured viscosity values. The temperature dependence of the intrinsic viscosity can be represented by a master curve in a versus |τ|M _w^1/2 (g^1/2 mol^−1/2) plot, where τ = |T − Θ|/T is the reduced temperature and M_w‐is the weight‐average molecular weight. A universal plot of reduced viscosity versus reduced blob parameter (N/N_c) shows the attainment of the collapsed state below the theta temperature. The dimensions of PMMA in acetonitrile (M_w = 3.15 × 10⁶ g mol⁻¹) decrease to 63 % at 26 °C of those in the unperturbed state. The results in this work are compared with those previously published. © 2000 Society of Chemical Industry     

Polybenzimidazole (PBI) molecular weight and Mark‐Houwink equation

The molecular weight, and intrinsic viscosity of polybenzimidazole (PBI) and its phosphonylated derivatives are reported. The relationship between intrinsic viscosity [η] and weight average molecular weight (M_w) for PBI has been established in H₂SO₄ and DMF‐LiCl. The Mark Houwink constants K_w of 5.2 × 10^?3 mL/g, α of 0.92 for H₂SO₄ solvent systems and, K_w of 3.2 × 10^?2 mL/g, α of 0.754 for DMF‐LiCl solvent system have been determined at M_w < 65,000. The intrinsic viscosity of PBI determined by the Huggins–Kraemer method was compared with a single point method, and found that both methods fit well for PBI in relatively low concentration solvent system, giving ～ 99% accuracy. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Moisture retention and antibacterial activity of modified chitosan by hydrogen peroxide

A series of chitosans with various molecular weights from 1.2 × 10³ to 30.0 × 10⁴ were prepared by oxidative degradation with H₂O₂ and characterized by IR, ¹³C‐NMR, and gel permeation chromatography. Their carboxylic contents increased with a decrease in molecular weight (M_w). The moisture‐absorption and moisture‐retention capacities of resulting chitosans were dependent on both the molecular weight and the degree of deacetylation (DD). Microcalorimetry was first used to study the kinetics of action of the chitosans on a strain of Staphylococcus aureus at pH 7. The antibacterial activity of the water‐soluble chitosan against S. aureus, Escherichia coli, and Salmonella typhi was evaluated by the conventional agar plate method at pH 7. The water‐soluble product with M_w of 0.45 × 10⁴ from initial chitosan of DD of 90% showed high moisture‐absorption and moisture‐retention capacities, and <2% concentration can completely inhibit the growth of these bacteria. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1724–1730, 2002     

Microbiocidal activity of chitosan‐N‐2‐hydroxypropyl trimethyl ammonium chloride

Chitosan‐N‐2‐hydroxypropyl trimethyl ammonium chloride (QTS) was prepared by reaction of chitosan with glycidyl trimethylammonium chloride, which was characterized by FTIR. QTS with different molecular weights (M_w 41.55 × 10⁴, 9.02 × 10⁴, 3.57 × 10⁴, and 0.17 × 10⁴) showed biocidal activity on Staphylococcua aureus, Bacillus subtilis, Staphylococcua epidermidis, and Candida albicans. QTS with high molecular weight had high biocidal activity on the gram‐positive bacteria, and the biocidal effect of QTS decreased with decreasing molecular weight from 9.02 × 10⁴ to 0.17 × 10⁴. QTS with M_w 41.55 × 10⁴ exhibits slightly lower biocidal activity on Candida albicans than other QTS samples. However, no remarkable biocidal activity of QTS was found on gram‐negative bacteria Escherichia coli and Pseudomonas aeruginosa at the concentration up to 10 g L^?1. Existence of cationic surfactant, amphoteric surfactant, nonionic surfactant, Ca²⁺ and Mg²⁺ had no remarkable effect on microbiocidal activity of these QTS samples. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3851–3856, 2007     

Effects of the molecular weight on the properties of thermoplastics prepared from soy protein isolate

Commercial soy protein isolate (SPI) was fractionated into four fractions by an acidifying method from pH 5.7 to 4.5 with 2M HCl. A mixture of SPI with glycerin (50 g/100 g of dry SPI) was compression‐molded to obtain thermoplastic sheets. The weight‐average molecular weight (M_w) of the fractions, the structure, and the mechanical properties of the thermoplastic SPI sheets were investigated with light scattering, IR spectroscopy, wide X‐ray diffraction patterns, differential scanning calorimetry, ultraviolet spectroscopy, scanning electron microscopy, and tensile testing. After heating compression, the SPI sheets were transparent and exhibited a smooth and homogeneous structure. Moreover, the crystallinity degree of the thermoplastic SPI was obviously higher than that of the premix before compression because of the formation of intermolecular hydrogen bonding. The M_w's of the fractions were 1.17 × 10⁵ to 3.21 × 10⁵, and they increased with increasing pH value in fractionation. The mechanical properties and water resistance (R) of the SPI sheets increased with increasing M_w of the SPI fractions. The tensile strength and breaking elongation of the SPI sheets with an M_w value of 3.21 ×10⁵ were 5.7 MPa and 135%, respectively, and the R value was 0.54 after immersion in water for 15 days. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3373–3380, 2001     

Synthesis and properties of new novolacs based on heteroatom‐bridged phenol derivatives

We describe the synthesis and properties of new novolacs prepared by addition‐condensation of heteroatom‐bridged phenol derivatives and formaldehyde. The trifluoroacetic acid‐catalyzed polymerization of equimolar amounts of bis(4‐methoxyphenyl) ether ( 1a ) and formaldehyde proceeded homogeneously to afford the polymer ( 2a ) in 49% yield (M_n 2600, M_w/M_n 1.8). From the FTIR, ¹H‐NMR, and ¹³C‐NMR spectra of 2a , it was evident that the polymer had methylene moieties‐bridged repeating units in the polymer backbone. A higher molecular weight novolac ( 2a ′) (yield 99%, M_n 16,600, M_w/M_n 12.9) could be prepared by using an excess of formaldehyde. Bis(4‐methoxyphenyl) sulfone novolac ( 2b ) (M_n 1300, M_w/M_n 1.2) and bis(4‐methoxyphenyl) sulfide novolac ( 2d ) (M_n 1200, M_w/M_n 1.9) were also prepared. However, the polymerization of bis(4‐hydroxyphenyl) sulfone ( 1c ) did not proceed, even when it was attempted under various reaction conditions. From TGA, the temperatures at 10% loss in weight (T₁₀) for 2a , 2a ′, and 2b were found to be 413, 430 and 393°C, respectively. These results suggested that heteroatom‐bridged novolacs based on phenol derivatives have good thermal stability than other organosoluble polymers; moreover, these novolacs could be expected to function as processable materials, polymer blends for engineering plastics, etc. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009