Progress of Polymerization of D,L-Lactide Through Differential Scanning Calorimetry and Gel Permeation Chromatography

Melt polymerization conditions for D,L-lactide initiated with tetraphenyltin were studied with regard to polymer molecular weight. The present study was undertaken to investigate the progress of polymerization of D,L-lactide through differential scanning calorimetry (DSC), and also to explore the correlation between melt polymerization conditions and molecular weight. The physical characteristics, such as glass transition temperature (Tg) of the polymer and melting transition (Tm) of D,L-lactide are correlated with GPC data. DSC data shows that the Tm of D,L-lactide is 122.8 at 150°C polymerization time. ΔHf is 83.2 J g-1, and Tg of polymer is untraceable. At 180°C the Tm is 101.4°C, ΔHf is 34 J g-1, and Tg is around 29.5°C. The drop in Tm and ΔHf clearly shows the conversion of D,L-lactide to polymer. The maximum increment to molecular weight of polymer is achieved at 160°C and 8 h. After a short induction period, the slow polymerization of D,L-lactide resulted in maximal molecular weight followed by an almost constant value of molecular weight. This revised version was published online in July 2006 with corrections to the Cover Date.     

Processable Heat-Resistant Polymers. IX. Synthesis and Properties of Polyamideimide from N-(p-Carboxy Phenyl) Trimellitimide and p,p′-Di-(amino Phenyl) Sulfone

A novel polyamideimide was synthesized by reacting p,p′-di-(amino phenyl) sulfone and N-(p-carboxy phenyl) trimellitimide or its diacid chloride derivative. The polymer was found to be soluble in highly polar solvents. The polymer was characterized by elemental analyses and IR spectrum. It is found to be amorphous and of low molecular weight. The polymer is fairly thermostable, having a T of 210–220°C. Thermogravimetric determination revealed that the polymer underwent 17% weight loss at 375°C in air. The dielectric constant of the polymer at 1 kHz was 3.74 at 30°C. The electrical conductivity of the polymer was also measured.     

Characterization, Solution Behavior, and Microstructure of a Hydrophobically Associating Nonionic Copolymer

To obtain an oil-displacement polymer with good thermal stability and solution properties, self-assembling acrylamide (AM)/4-butylstyrene (BST) copolymers (PSA) were synthesized by the micellar copolymerization technique. The resulting polymer was characterized by elemental analysis and UV and FT-IR spectroscopy. Conventional DSC measurement was used successfully to characterize the hydrophobic microblock structure of PSA, and two glass transition temperatures were found in the polymer: at 203 °C for the AM segments and at 106 °C for the hydrophobic BST segments. The initial decomposition temperature (234 °C) of the polymer is higher than that of polyacrylamide (210 °C). The DSC and TG results suggest that incorporation of BST into PSA enhances the molecular rigidity and thermal stability of the polymer. The apparent viscosity of a PSA solution greatly depends on the amount of BST in the polymer, and the polymer exhibits salt-thickening, temperature-thickening, thixotropy, pseudo-plastic behavior, anti shearing, and good anti-aging properties at 80 °C. In addition, the apparent viscosities of PSA solutions are increased remarkably by the addition of a small amount of surfactant. AFM measurements show that large block-like aggregates and small compact aggregates are formed in aqueous solutions of 0.4 g⋅dL⁻¹ PSA because of strong intermolecular hydrophobic associations, despite the low molecular weight, and their sizes increase upon addition of a small amount of salt.     

Synthesis and Characterization of Poly(allyl methacrylate) Obtained by Free Radical Initiator

Allyl methacrylate was polymerized in CCl₄ solution by α,α′‐azoisobutyronitrile at 50, 60, and 70°C. The kinetic curves were auto‐accelarated types at 60 and 70°C, but almost linear at 50°C. Arrhenius activation energy was 77.5 kJ/mol. The polymer was insoluble in common organic solvents. It was characterized by FT‐IR, NMR, DSC, TGA and XPS methods. About 98–99% of allyl side groups were remained as pendant even after completion of the polymerization. The spectroscopic and thermal results showed that polymerization is not a cyclopolymerization type, but may have end group cyclization. The high molecular weight is the main cause of a polymer being insoluble even in the early stage of the polymerization. Molecular weight of 1.1×10⁶ for a soluble polymer fraction was measured by light scattering method. The Tg of polymer was 94°C, and after curing at 150–200°C, increased to 211°C. The thermal pyrolysis of polymer at about 350°C gave an anhydride by linkage type degradation, and side group cyclization. The XPS analysis showed the presence of radical fragments of AIBN (initiator) and CCl₄ (solvent) associated with oligomers.     

Polymerization and polymer properties of (p-tert-butyl-o,o-dimethylphenyl)acetylene

(p-tert-Butyl-o,o-dimethylphenyl)acetylene (BDMPA) polymerized in high yields in the presence of W and Mo catalysts. Especially the W(CO)₆–CCl₄–hv catalyst quantitatively produced a polymer totally soluble in toluene and chloroform. The weight-average molecular weight of this polymer exceeded 2 × 10⁶. Poly(BDMPA) was a dark brown solid, and had alternating double bonds along the main chain. The weight loss of the polymer in air occurred only above 300°C, indicating a fairly high thermal stability. A free-standing film could be fabricated by solution casting. The electrical conductivity of the polymer at 25°C was 1 × 10⁻¹³ S cm⁻¹. The oxygen permeability coefficient and the separation factor of O₂ vs. N₂ of the polymer at 25°C were 67 barrers and 3.2, respectively. © 1996 John Wiley & Sons, Inc.     

Synthesis and properties of semi-interpenetrating network based on styrene-acrylonitrile-vinyl acetate terpolymer and zinc acrylate

Semi-Interpenetrating polymer network materials (semi IPNs) have been synthesized from styrene-acrylonitrile-vinyl acetate terpolymer as polymer I and zinc acrylate as polymer II, using divinyl benzene as crosslinking agent for polymer II. The terpolymer was pre-synthesized by a radical polymerization method using AIBN as the radical initiator. The terpolymer has been characterized by IR and elemental analysis. The composition (Sty: AN:VAc) = (0.25:0.50:0.25), the intrinsic viscosity (0.16 dl/g), the softening temperature range (180–185 °C), the glass transition temperature (23 °C) and the thermal stability (up to 300 °C) of the terpolymer were determined. The IPN was characterized by determining its density (1.12 g/cc at 30 °C), molecular weight between crosslinks (M_c = 1469), thermal stability (~ 400 °C), glass transition temperature (41 °C, 78 °C) and two-phase morphology.     

Association of polyacrylonitrile prepared by low-temperature,solution polymerization with an organometallic catalyst

The weight-average molecular weights of polymers of acrylonitrile prepared by a free-radical initiator and an organometallic catalyst have been determined by lightscattering measurements in N,N-dimethylformamide, dimethyl sulfoxide, and dimethylacetamide at 25°C. and in dimethyl sulfoxide at 140°C. The apparent molecular weights of the polymers prepared with the NaAlEt₃S(i-Pr) catalyst in DMF at ?78°C. (referred to as high-melting polymers) changed from 54,800, 82,700, and 480,000 when measured in DMF at 25°C. to 36,000, 41,600, and 225,000 when measured in DMSO at 140°C., whereas the molecular weights of the free-radical polymers remained unchanged. Furthermore, from results obtained in DMSO at 140°C., The intrinsic viscosity–molecular-weight relationships were found to be identical for the high-melting and the free-radical polymer and in substantial agreement with an equation reported by Cleland and Stockmayer. The apparent decrease in molecular weight of the high-melting polymer from 25 to 140°C. indicates rather clearly that the high-melting polymers are associated in DMF at 25°C. The “aggregates,” even though present only at low concentrations, raised the weight-average molecular weight markedly but affected the number-average molecular weight only slightly, thus giving a high M?_w/M?_n ratio. It appears likely that when temperature and solvent are such that association does not occur, linear PAN's will have approximately the same intrinsic viscosity–molecular weight relationship (subject of course to slight change by polydispersity). The often reported abnormal molecular weight of samples prepared by solution polymerization especially at low temperatures, may be attributed to branching, or to an association, as reported here. The nature of association of PAN in dilute solution is also discussed.     

Synthesis and characterization of poly[4-(4-hydroxyphenoxy) benzoic acid]

Poly[4-(4-hydroxyphenoxy) benzoic acid] was prepared by the bulk polycondensation of 4-(4-acetoxyphenoxy) benzoic acid. Polycondensation was conducted at 350°C for 3 h under a reduced pressure of 0.1 mmHg and gave a polymer with X?n of 255. The polymer was characterized by elemental analysis, IR spectroscopy, differential scanning calorimetry, and wide-angle X-ray measurement. The crystal/nematic and nematic/isotropic phase transition temperatures of polymer, which depend on the molecular weight, were observed at about 300°C and 410°C, respectively. The polymers with low molecular weights showed nematic textures above 300°C. This nematic/isotropic phase transition temperature is lower than that of poly (4-hydroxybenzoic acid). This thermal behavior of polymer comes from ether units, which increase the flexibility (the rotation or torsion of skeletal bonds) of the polymer chain. © 1994 John Wiley & Sons, Inc.     

Synthesis of polyphthalimidines with benzylidene group from aminophthalide monomers

Two aminophthalide monomers, 6-amino-3-benzylidenephthalide (I) and 3-(p-aminobenzylidene)phthalide (II), underwent self-polycondensation in o-phenylphenol at 250°C to yield polyphthalimidines with inherent viscosities up to 0.5 dL/g. These polymers were readily soluble in a variety of solvents such as dimethylformamide, dimethyl sulfoxide, m-cresol, pyridine, and methylene chloride. The temperatures at which a 10% weight loss occurred by thermogravimetry in nitrogen were 460°C for the polymer derived from I and 490°C for the polymer from II. The glass transition temperature of the polymer from I was 332°C, determined by thermomechanical analysis.     

Electrochromic material containing unsymmetrical substituted N,N,N′,N′‐tetraaryl‐1,4‐phenylenediamine: Synthesis and their optical,electrochemical, and electrochromic properties

A novel dibromo compound containing unsymmetrical substituted bi‐triarylamine was synthesized. A conjugated polymer was prepared via the Suzuki coupling from the newly prepared dibromo compound and 9,9‐dioctylfluorene‐2,7‐bis(trimethyleneboronate). The glass transition temperature (T_g) of the conjugated polymer was 140 °C, 10% weight‐loss temperatures (T_d10) in nitrogen was 458 °C, and char yield at 800 °C in nitrogen higher than 64%. Cyclic voltammogram of the polymer film cast onto an indium‐tin oxide (ITO)‐coated glass substrate exhibited two reversible oxidation redox couples at 0.70 and 1.10 V versus Ag/Ag⁺ in acetonitrile solution. The polymer films revealed excellent stability of electrochromic characteristics, with a color change from yellow green of the neutral form to the dark green and blue of oxidized forms at applied potentials ranging from 0 to 1.3 V. The color switching time and bleaching time were 4.25 and 7.22 s for 860 nm and 5.51 s and 6.48 s for 560 nm. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1469–1476, 2010     

Synthesis and characterization of poly[3,5′-(3-pyridyl methyl)-2,6,-diaminotoluene] and its condensation product,poly[4-(3-pyridyl),8-methyl,2,3-6,7-quinolino]

2,6-Diaminotoluene was reacted with 3-pyridinecarboxaldehyde in acidic medium and the intermediate polymer was further condensed in polyphosphoric acid at high temperature (335°C) to obtain a soluble heterocyclic ladder polymer, poly[4-(3-pyridyl),8-methyl,2,3–6,7-quinolino] (PPMQ). The molecular weight of the intermediate polymer depended on the reaction temperature and the rate of reactant addition. The NMR spectra of the intermediate polymer indicated that a linear polymer with resonable molecular weight was formed. Element analysis and IR spectra confirmed the structure of the final polymer.     

Radical polymerization and copolymerization of methyl α-(2-carbomethoxyethyl)acrylate,a dimer of methyl acrylate,as a polymerizable α-substituted acrylate

Polymerization and copolymerization of methyl α-(2-carbomethoxyethyl)acrylate (MMEA), which is known as a dimer of methyl acrylate, were studied in relation to steric hindrance-assisted polymerization. The propagating polymer radical from MMEA was detected as a five-line spectrum and quantified by ESR spectroscopy during the bulk polymerization at 40–80°C. The absolute rate constants of propagation and termination (κ_p and κ_t) for MMEA at 60°C (κ_p = 19 L/mol s and κ_t = 5.1 × 10⁵ L/mol s) were evaluated using the concentration of the propagating radical at the steady state. The balance of the propagation and termination rates allows polymer formation from MMEA. The polymerization rate of MMEA at 60°C was less than that of MMA by a factor of about 4 at a constant monomer concentration. Although no influence of ceiling temperature was observed at a temperature ranging from 40 to 70°C, addition-fragmentation in competition with propagation reduced the molecular weight of the polymer. The content of the unsaturated end group was estimated to be 0.1% at 60°C to the total amount of the monomer units consisting of the main chain. MMEA exhibited reactivities almost similar to those of MMA toward polymer radicals. It is concluded that MMEA is one of the polymerizable acrylates bearing a substituted alkyl group as an α-substituent. Characterization of poly(MMEA) was also carried out. © 1996 John Wiley & Sons, Inc.     

Radiation-induced ionic polymerization of isobutyl vinyl ether in bulk

The radiation-induced ionic polymerization of isobutyl vinyl ether was investigated under conditions where the monomer was dried with molecular sieves. The investigation covered the temperature range from ?16°C to 90°C, and the dose-rate range from 10¹⁵ to 10²⁰ eV/g-sec, using both γ-rays and electrons. A very high overall activation energy of 15.9 kcal/mole was found for the process below 30°C. Above 30°C, however, the value of the overall activation energy dropped to 4.9 kcal/mole, a phenomenon which is ascribed to the solvation of the propagating carbonium ion below 30°C. The dose-rate dependence of the rate of polymerization was found to be 0.58 over the entire dose-rate range investigated. The molecular weight of the polymer was found to be far less sensitive to trace amounts of water than the rate of polymerization. The molecular weight of the polymer depended strongly on the irradiation temperature, reaching a maximum value of about 120,000 at 35°C. It is shown that at temperatures above 20°C regenerative chain transfer processes play an important role in determining the molecular weight of the polymer.     

Synthesis of photoreactive isopropyl-substituted poly(phenylene ether ether ketone)

Isopropyl substituted poly(phenylene ether ether ketone) with a high molecular weight was prepared by nucleophilic substitution reaction of isopropyl-substituted difluoro diaryl ether with hydroquinone. This polymer was amorphous and soluble in common organic solvents, such as THF, chloroform, and cyclohexanone. Thermogravimetry of the polymer showed good thermal stability, indicating that a 10% weight loss of the polymer was observed at 470°C in nitrogen. The glass transition temperature of the polymer was 145°C. The polymer had a broad UV absorption band over 250–380 nm. The polymer acted as a photosensitive resist of negative type for UV radiation. The resist had a sensitivity of 40 mJ/cm² and a contrast of 2.8, when it was developed with DMF at room temperature. © 1997 John Wiley & Sons, Inc.     

The Effect of Active Carbon on the Kinetics of Polymerization of Methyl Methacrylate

Rates of 2–2¹?azobisisobutyronitrile initiated polymerization of methyl methacrylate in benzene were determined at 77.2, 65.0, and 50.0°C. The variation of molecular weight of the polymer with temperature and conversion was also studied. At a fixed conversion of 2.0%, the molecular weight decreased from 2.05 × 10⁵ at 50°C to 1.4 × 10⁵ at 77.2°C. The ratio of the propagation rate coefficient to the square root of the termination rate coefficient was found to be 0.61, 0.397, and 0.374 at 77.2, 65.0, and 50.0°C, respectively, with an uncertainty of ±0.5°C in temperature. The effect of active carbon on the rates of polymerization at 77.2°C was measured. Rates of polymerization decreased in the presence of active carbon. For example, the initial rate of polymerization decreased from 7.8 × 10^?4 mole/(liter min) to 4.6 × 10^?4 mole/(liter min) when the carbon concentration was varied from 0 to 9.65 g/liter. The molecular weight of the polymer increased from an average of 1.4 × 10⁵ in the absence of carbon to 1.5 × 10⁵ when carbon was present.     

Synthesis of perfluoro(methyl vinyl ether) polymer at high pressures

Polymer of perfluoro(methyl vinyl ether) was synthesized for the first time. Polymerization was carried out at pressures from 300 to 1500 MPa and temperatures from 80 to 200 °C. The polymer synthesized is elastic, transparent, and soluble in perfluorobenzene, perfluorodecalin, and other perfluorinated solvents. The intrinsic viscosity of the polymer reaches 2 dL g^s-1. The study of the thermal stability on a derivatograph showed that the weight loss of the polymer sample occurred at 372 °C, being 0.1%.     

Polymerization of o‐quinodimethanes. IV. Radical polymerization of 1‐cyano‐o‐quinodimethane in the presence of TEMPO

The radical polymerization behavior of 1‐cyano‐o‐quinodimethane generated by thermal isomerization of 1‐cyanobenzocyclobutene in the presence of 2,2,6,6‐tetramethylpiperidine‐N‐oxide (TEMPO) and the block copolymerization of the obtained polymer with styrene are described. The radical polymerization of 1‐cyanobenzocyclobutene was carried out in a sealed tube at temperatures ranging from 100 to 150 °C for 24 h in the presence of di‐tert‐butyl peroxide (DTBP) as a radical initiator and two equivalents of TEMPO as a trapping agent of the propagation end radical to obtain hexane‐insoluble polymer above 130 °C. Polymerization at 150 °C with 5 mol % of DTBP in the presence of TEMPO resulted in the polymer having a number‐average molecular weight (M_n ) of 2900 in 63% yield. The structure of the obtained polymer was confirmed as the ring‐opened polymer having a TEMPO unit at the terminal end by ¹H NMR, ¹³C NMR, and IR analyses. Then, block copolymerization of the obtained polymer with styrene was carried out at 140 °C for 72 h to give the corresponding block copolymer in 82% yield, in which the unimodal GPC curve was shifted to a higher molecular weight region. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3434–3439, 2000     

Photoinitiated polymerization of methacrylates comprising phenyl moieties

Investigation of photopolymerization kinetics of 4-(4-methacryloyloxyphenyl)-butan-2-one (1) in comparison with 2-phenoxyethyl methacrylate (2) and phenyl methacrylate (3) using a UV-LED emitting at 395 nm shows significantly faster polymerization of 1 compared to both 2 and 3 at 40°C. Vitrification affects photopolymerization kinetics of all methacrylates under investigation. Interestingly, quantitative final conversion is observed during photoinitiated polymerization of 1 and 2 whereas 3 shows limited conversion at about 80%. Furthermore, higher degree of polymerization is obtained by photoinitiated polymerization of 1 compared to 2 and 3. This shows that the 3-oxobutyl substituent at the phenyl ring of 1 significantly affects both polymerization kinetics and final conversion of the photoinitiated polymerization. Moreover, an additional higher molecular weight fraction is observed in case of polymerization of 1 at 85°C that is above the glass transition temperature of the polymer formed during photoinitiated polymerization. As a thermal polymerization at 85°C in the absence of light results in a high molecular weight polymer as well, an additional thermal process may be discussed as reason for the higher molecular weight polymer fraction in case of the photopolymer made at 85°C.     

Synthesis and characterization of aromatic poly(ether ketone)s containing cyclotriphosphazene units

Bis(4-oxybenzoic acid) tetrakis(phenoxy) cyclotriphosphazene (IUPAC name: 4-[4-(carboxyphenoxy)-2,4,6,6-tetraphenoxy-1,3,5,2λ⁵,4λ⁵,6λ⁵-triazatriphosphinin-2-yl]oxy-benzoic acid) was synthesized and direct polycondensed with diphenylether or 1,4-diphenoxybenzene in Eaton's reagent at the temperature range of 80–120°C for 3 hours to give aromatic poly(ether ketone)s. Polycondensations at 120°C gave polymer of high molecular weight. Incorporation of cyclotriphosphazene groups in the aromatic poly(ether ketone) backbone greatly enhanced the solubility of these polymers in common organic polar solvents. Thermal stabilities by TGA for two polymer samples of polymer series ranged from 390 to 354°C in nitrogen at 10% weight loss and glass transition temperatures (T_g) ranged from 81.4 to 89.6°C by DSC. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1227–1232, 1998     

Polyquinazolotriazoles

A novel high molecular weight (η_inh = 1.4 dl/g) polyquinazolotriazole (PQT) was prepared from the reaction of 3,3′-(2″,6″-pyridinediyl)bis[5-(o-aminophenyl)-1,2,4-triazole] with isophthalic acid by solution cyclopolycondensation in polyphosphoric acid, with diphenyl isophthalate by melt polycondensation, and with isophthaloyl chloride to form a precursor polyamide which subsequently underway cyclodehydration. Thermal characterization of the PQT by thermogravimetric analysis showed initial weight loss in air commencing at ～490°C. The PQT exhibited a weight loss of only 4% after aging in static air for 200 hr at 316°C and a T_g of 342°C as measured by differential scanning calorimetry. Prior to polymer synthesis, a series of model compounds was prepared as a guide to polymer synthesis and identification.