Emulsifier-free emulsion polymerization of tetrafluoroethylene by radiation. IV. Effects of additives on polymer molecular weight

Poly(tetrafluoroethylene) (PTFE) of high molecular weight, 4.5 × 10⁷, was incidentally obtained at earlier study of an emulsifier-free emulsion polymerization of tetrafluoroethylene by radiation. In order to clarify this phenomenon, the effects of additives, in particular radical scavengers, on the molecular weight of PTFE and its polymerization behavior were studied. It was found that the molecular weight of PTFE is increased by the addition of hydroquinone, benzoquinone, α-pinene, dl-limonene, and ethylenediamine but is decreased by oxygen and triethylamine. A PTFE latex with molecular weight higher than 2 × 10⁷ was obtained in the presence of hydroquinone. It is concluded that additives such as hydroquinone and benzoquinone, which rapidly scavenge the primary radicals (OH·, H·, and e_aq^?) in the aqueous phase but not the growing polymer radicals in PTFE particles, are most effective in increasing the molecular weight.     

A comparative study of characteristics of polytetrafluoroethylene fibers manufactured by various processes

A series of polytetrafluoroethylene (PTFE) fibers were manufactured by three processing methods including extrusion process, split‐sheet process and split‐film process. The influence of processing methods on fiber properties were systematically studied using four PTFE powders with various molecular weights (3.86 × 10⁷, 4.71 × 10⁷, 4.92 × 10⁷ and 5.11 × 10⁷, respectively). Morphology, crystallinity, tensile behavior and friction properties of PTFE fibers were compared by scanning electron micrograph, X‐ray diffraction pattern, strength‐elongation curves and friction coefficients, respectively. The results showed that the in terms of flat filaments, mechanical properties became weak with the increase of molecular weight of PTFE powders at first, but were improved dramatically with further enhancement of molecular weight. In the case of both round filaments and split‐film fibers, fiber properties were improved with growth of molecular weight. Based on characteristics and friction coefficients, potential applications of three types of PTFE samples were analyzed. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43553.     

Ring‐opening polymerization of ε‐caprolactone with a divalent samarium bis(phosphido) complex

The ring‐opening polymerization of ε‐caprolactone initiated with a divalent samarium bis(phosphido) complex [Sm(PPh₂)₂] is reported. The polymerization proceeded under mild reaction conditions and resulted in polyesters with number‐average molecular weights of 8.2 × 10³ to 12.5 × 10³. The yield and molecular weight of poly(ε‐caprolactone)s were dependent on the experimental parameters, such as the monomer/initiator molar ratio, the monomer concentration, the reaction temperature, and the polymerization time. The obtained polymers were characterized with Fourier transform infrared, NMR, gel permeation chromatography, and differential scanning calorimetry. On the basis of an end‐group analysis of low‐molecular‐weight polymers by NMR spectroscopy, a coordination–insertion mechanism is proposed for the polymerization. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1558–1564, 2005     

Morphology of poly(hexamethylene oxide) fractions

The supermolecular structure of crystallised molecular weight fractions of poly(hexa-methylene oxide), covering the molecular weight range (M) 4.5. × 10³ to 8. 5 × 10⁴, was studied by polarised light microscopy and small angle light scattering. Different forms were observed as a function of molecular weight and crystallisation temperatures. Perfect spherulites are formed after rapid crystallisation, and these forms deteriorate as both the molecular weight and crystallisation temperature increase. The morphology in the isothermal crystallisation region corresponds to an intermediate state which represents a transition from spherulites to hedrites.     

Number-average molecular weight of radiation-degraded poly(tetrafluoroethylene). An end group analysis based on solid-state NMR and IR spectroscopy

Changes in the chemical structure of poly(tetrafluoroethylene) (PTFE) induced by electron beam irradiation at room temperature in air have been studied by ¹⁹F solid-state NMR and IR spectroscopy. Chain scission associated with the formation of trifluoromethyl (-CF₃), carboxylic acid fluoride (-COF) and carboxylic acid (-COOH) end groups was confirmed to be the predominant process under these conditions. The number-average molecular weight of radiation-degraded PTFE as a function of irradiation dose was calculated based on quantitative end group analysis. It strongly decreases with increasing dose to approximately 4000 g/mol at a irradiation dose of 4 MGy. The molar ratio of CF₃ end groups to oxygen-containing (-COF, -COOH) end groups was found to depend on the irradiation dose and the irradiation conditions. For low dose level, the molar ratio determined experimentally coincides well with the mechanism proposed for radiation-induced degradation of PTFE.     

Effect of stoichiometric imbalances on the melt condensation polymerization of poly(dodecamethylene terephthalamide) studied by intrinsic viscosity and 13C‐NMR

Poly(dodecamethylene terephthalamide) (PA‐12,T) was synthesized by melt condensation polymerization of 12,T salt with 0, 1, 3, 5, or 10% molar excess of 1,12‐diaminododecane (DA), terephthalic acid (TA), or benzoic acid (BA). Intrinsic viscosities (IV) (0.5 g/dL in 96% H₂SO₄ at 25°C) were measured to determine relative molecular weight differences. IV was highest for reactions containing 1 and 3 mol % excess DA (1.36 and 1.31 dL/g, respectively), followed by the product of pure 1 : 1 salt (1.25 dL/g). For all concentrations of excess TA and BA, IV was decreased. ¹³C‐NMR chemical shifts for DA, TA, and BA end groups were identified and their concentrations determined by comparison with the intensity of main chain polymer peaks. A log–log plot of IV versus number average molecular weight calculated from ¹³C‐NMR data shows a linear trend with Mark‐Houwink constants of K = 55.8 × 10^?5 dL/g and α = 0.81. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Carbon‐13 NMR,GPC, and DSC study on a propylene‐1‐butene copolymer fractionated by temperature rising elution fractionation

A random copolymer of propylene with small amounts of 1‐butene comonomer, synthesized with a Ziegler–Natta catalyst, was fractionated by temperature rising elution fractionation (TREF) to systemically investigate the fraction samples' molecular microstructure, as well as their relationship to the melting and crystallization behavior. First, TREF was employed to fractionate the sample, and then crystallization analysis fractionation (Crystaf) was used to check the effect of the TREF experiment. In the characterization of the molecular microstructure, carbon‐13 NMR spectroscopy (¹³C NMR) and gel permeation chromatography (GPC) experiments gave the following results: the fraction samples have relatively uniform molecular microstructure; with an increase in elution temperature, the 1‐butene content in the fraction samples decreases, but the molecular weight (M_n) and number average sequence length of propylene (n?_P) increase. In the study on melting and crystallization behavior, differential scanning calorimetry (DSC) experimental results show that the melting temperature increasingly decreases with an increase in 1‐butene content; however, dependence of the melting temperature on molecular weight becomes weaker and weaker with an increase in the number average molecular weight in the range of number average molecular weight below 1.82 × 10⁵ g/mol. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 845–851, 2006     

Synthesis and solution properties of novel nonionic functional polyurethane surfactants

A series of novel nonionic functional polyurethane surfactants were synthesized by the polycondensation of 2,4‐toluene diisocyanate with poly(propylene oxide) (weight‐average molecular weight = 400, 1000, or 2000) and monoallyl‐end‐capped poly(ethylene oxide). The chemical structure of the polyurethane surfactants was determined by Fourier transform infrared and ¹H‐NMR, and the effects of the concentration, salt, rest time, and temperature on the surface tension were investigated. These polymeric surfactants exhibited excellent surface activity. Sample III, which was synthesized with monoallyl‐end‐capped poly(ethylene oxide) (number‐average molecular weight = 1000), poly(propylene oxide) (number‐average molecular weight = 2000), and tolylene diisocyanate, could reduce the surface tension to 37.6 mN/m at a concentration of 0.06 mol/L at 25°C. All polyurethane surfactants synthesized in this study had low critical micelle concentrations (ca. 10^?4 to 10^?5 mol/L) and could reduce the surface tension even at very low concentration levels. Moreover, the surface tension decreased with an increase in the temperature or the concentration of the polyurethane surfactants. The addition of salt resulted in a decrease in the surface tension, and it took some time for the polyurethane surfactants to reach a constant surface tension value. UV spectra were found to be very useful for determining the critical micelle concentration. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2956–2962, 2006     

Bestimmung des molekulargewichts von „mikrogelhaltigem”︁ polystyrol mit der ultrazentrifuge (methode archibald)

The weight average molecular weight M_w of a mixture of two polystyrenes with very high and relatively low molecular weights (M_w = 16.1 · 10⁶ and 98 · 10³ g/mole), as a model for polymers containing microgel, was determined by ultracentrifugation with the ARCHIBALD-methode. M_w decreases with increasing number of rotation N. The exact molecular weight can only be determined by extrapolation to N = 0. This value depends nearly completely on the molecular weight and weight percentage of the “microgel”. It is not suitable for the characterization of the whole sample.     

Primary amine functionalized polystyrenes by atom transfer radical polymerization

Primary amine functionalized polystyrenes were prepared in quantitative yields by atom transfer radical polymerization using the adduct of 1‐(bromoethyl)benzene with 1‐(4‐aminophenyl)‐1‐phenylethylene as initiator for styrene polymerization in the presence of a copper(I) bromide/N,N,N′,N′,N″‐pentamethyldiethylenetriamine catalyst system. The polymerizations proceeded via a controlled free radical polymerization process to afford quantitative yields of the corresponding primary amine functionalized polystyrenes with predictable molecular weights (M_n = 2 × 10³ to 10 × 10³ g mol^?1), relatively narrow molecular weight distributions (M_w/M_n = 1.03–1.49), well defined chain‐end functionalities and initiator efficiencies as high as 0.92. The polymerization process was monitored by gas chromatographic analysis. The primary amine functionalized polymers were characterized by thin layer chromatography, size exclusion chromatography, potentiometry and spectroscopy. Experimental results are consistent with quantitative functionalization via the 1,1‐diphenylethylene derivative. Polymerization kinetic measurements show that the polymerization reaction follows first order rate kinetics with respect to monomer consumption and the number average molecular weight increases linearly with monomer conversion. © 2003 Society of Chemical Industry     

Molecular Structure Models of Asphaltene in Crude and Upgraded Bio‐Oil

The average molecular formula of asphaltene was calculated from the main functional groups of asphaltene determined by Fourier transform infrared spectroscopy, the average molecular weight found by gel filtration chromatography, and values of ultimate analysis. A series of average structure parameters were determined by ¹H NMR and ¹³C NMR spectrum integrals, followed by establishing the structure models of asphaltene according to the Brown‐Ladner method. Reduction of molecular weight of asphaltene was observed after bio‐oil upgrading, and the oxygen‐containing functional groups were apparently less than that of crude bio‐oil while the number of aromatic rings was increased. The upgraded bio‐oil had a lower molecular weight, lower oxygen content, and higher aromaticity compared with crude bio‐oil.     

Synthesis and characterization of the biomaterial poly(lactic acid‐co‐Nε‐carbobenzoyloxy‐L‐lysine) via direct melt copolymerization

With D,L ‐lactic acid and N^ϵ‐carbobenzoyloxy‐L ‐lysine [Lys(Z)] as the starting monomer material and tin dichloride as the catalyst, the drug carrier material poly(lactic acid‐co‐N^ϵ‐carbobenzoyloxy‐L ‐lysine) was synthesized via direct melt polycondensation. The copolymer was systematically characterized with intrinsic viscosity testing, Fourier transform infrared spectroscopy, ¹H‐NMR, gel permeation chromatography, differential scanning calorimetry, and X‐ray diffraction. The influences of different feed molar ratios were examined. With increasing molar feed content of Lys(Z), the intrinsic viscosity, weight‐average molecular weight, and polydispersity index (weight‐average molecular weight/number‐average molecular weight) gradually decreased. Because of the introduction of Lys(Z) with a big aromatic ring into the copolymer, the glass‐transition temperature gradually increased with increasing feed charge of Lys(Z), and all of the copolymers were amorphous. The copolymers, with weight‐average molecular weights from 10,500 to 6900 Da, were obtained and could reach the molecular weight level of poly(lactic acid) modified by Lys(Z) via the ring‐opening polymerization of the cyclic intermediates, such as lactide and morpholine‐2,5‐dione. However, a few terminal carboxyl groups might have been deprotected during the polymerization reaction under high temperatures. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Poly(ether urethane)s from aromatic diisocyanates based on lignin‐derived phenolic acids

A series of new bio‐based aromatic diisocyanates, namely bis(4‐isocyanato‐2‐methoxyphenoxy)alkane and bis(4‐isocyanato‐2,6‐dimethoxyphenoxy)alkane, were synthesized starting from lignin‐derived phenolic acids, namely vanillic acid and syringic acid, via the Curtius rearrangement. The diisocyanates were employed to synthesize poly(ether urethane)s by reacting them with potentially bio‐based aliphatic diols, namely 1,10‐decanediol and 1,12‐dodecanediol. The chemical structures of diisocyanates and poly(ether urethane)s were confirmed using Fourier transform infrared, ¹H NMR and ¹³C NMR spectroscopy. Inherent viscosities and number‐average molecular weights of the poly(ether urethane)s were in the ranges 0.58–0.68 dL g^?1 and 32 100–58 500 g mol^?1, respectively, indicating the formation of reasonably high molecular weight polymers. The poly(ether urethane)s exhibited 10% weight loss in the temperature range 304–308 °C. The glass transition temperatures of the poly(ether urethane)s were in the range 49–74 °C and were dependent both on the number of methylene units in the diols and on the number of methoxy substituents on the aromatic rings of the diisocyanate component. © 2017 Society of Chemical Industry     

Synthesis of poly(dodecyl methacrylate)s and their drag‐reducing properties

Dodecyl methacrylate was synthesized as the intermediate monomer for the preparation of poly(dodecyl methacrylate)s, which were synthesized with emulsion polymerization techniques. The intrinsic viscosities were measured, and the viscosity‐average molecular weights were calculated. Polymers of dodecyl methacrylate with ultrahigh molecular weights (viscosity‐average molecular weight > 10⁷) were synthesized through orthogonal experiments. The drag‐reduction properties of these polymers were studied in kerosene. The drag‐reducing behavior of these polymers exhibited a strong dependence on the molecular weight and Reynolds number, and these polymers could be used as effective oil‐soluble drag reducers and had good shear stabilities. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1622–1626, 2003     

Effect of polymer chain length on the solubility of polystyrene grafted single‐walled carbon nanotubes in tetrahydrofuran

BACKGROUND: While carbon nanotubes are highly interesting materials for a variety of applications, their inherent insolubility limits widespread applications and solution‐phase processing. It is known that chemical functionalization can overcome this insolubility problem, and covalent grafting of polymers to the nanotube surface has been shown to be effective. In this study, the effect of polymer molecular weight on the solubility of polymer–nanotube conjugates was investigated. RESULTS: A series of nitroxide‐capped polystyrene polymers ranging in molecular weight from 2900 to 105 000 g mol^?1 were grafted to single‐walled carbon nanotubes (SWNTs). The resulting polystyrene–SWNT conjugates exhibited different degrees of solubility in tetrahydrofuran. Subsequent thermogravimetric and UV‐visible spectroscopy analyses indicated that carbon nanotube solubility reached a maximum when a polymer sample with a weight‐average molecular weight of 10 000 g mol^?1 was used. Higher and lower molecular weights resulted in reduced solubilities. CONCLUSION: Polymer chains of intermediate length maximize SWNT solubility, while lengths that are too low or too high seem to diminish the ability of the polymer–SWNT conjugates to remain in solution. Copyright © 2008 Society of Chemical Industry     

Effects of drawing conditions on the properties of optical fibers made from polystyrene and poly(methyl methacrylate)

Monofilaments possessing various degrees of birefringence were obtained by changing the drawing rate, the molten polymer temperature, and the molecular weight of polystyrene (PS) and poly(methyl methacrylate) (PMMA). The “brittle-toductile” transition point of optically pure PS was found in the range of birefringences of ?0.6 · 10^?3 to ?2.6 · 10^?3. Both the height and position of this point are influenced by M?_w, molecular weight distribution, and polymer melt temperature. The birefringence of PS is higher by two orders of magnitude than that of PMMA in which this transition point has not been observed. The mechanical and optical properties depend not only on the average amount of orientation characterized by the birefringence but on what portion of the relaxation spectrum of the polymer is preferentially oriented. During the drawing of PS and PMMA monofilaments crazes are formed in the centre of the fibers and do not reach the surface.     

Rapid ambient temperature living radical polymerization of methyl methacrylate and styrene utilizing sodium hypophosphite as reducing agent

A facile, safe, and inexpensive reducing agent, sodium hypophosphite (NaH₂PO₂·H₂O), has been successfully used to perform ambient temperature living radical polymerizations of methyl methacrylate (MMA) and styrene (St). The rapid radical polymerizations were readily obtained at 25°C, i.e., MMA reached a conversion of ca 90% after 2.5 h, and St reached a conversion of ca 80% after 40 h. The polymerizations of MMA and St exhibited excellent living/controlled nature, as evidenced by pseudo first‐order kinetics of polymerization, linear evolution of molecular weights with increasing monomer conversions, and narrow molecular weight distributions. The various experimental parameters—ligand, solvent, and molar ratio of NaH₂PO₂·H₂O to CuSO₄·5H₂O—were varied to improve the control of polymerization, molecular weight, and molecular weight distribution. ¹H NMR analyses and chain‐extension reactions confirm the high chain‐end functionality of the resultant poly(methyl methacrylate) and polystyrene. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42123.     

Emulsion polymerization of tetrafluoroethylene: effects of reaction conditions on the polymerization rate and polymer molecular weight

The emulsion polymerization of tetrafluoroethylene (TFE) was carried out in a semibatch reactor using a chemical initiator (ammonium persulfate) and a fluorinated surfactant (FC-143). The effects of the reaction condition were investigated though the polymerization rate, molecular weight of polytetrafluoroethylene (PTFE), and stability of the dispersion. The emulsion polymerization of TFE was different from conventional emulsion polymerization. The polymerization rate was suppressed when the polymer particles were significantly coagulated. The polymerization rate increased with operating temperature, surfactant concentration, and agitation speed, due to the enhanced stability of the polymer particles. However, once the parameter value was reached, the rate decreased due to the coagulation of the particles. Stable PTFE dispersion particles were obtained when the surfactant concentration was in the range between 3.48 × 10⁻³ and 32.48 × 10⁻³ mol/liter, which is below critical micelle concentration (CMC). The molecular weight of the PTFE obtained was a function of the surfactant and initiator concentrations, and the polymerization temperature. The molecular weight increased as each parameter decreased. This is against the phenomena observed in a conventional emulsion polymerization. A stable PTFE dispersion polymer having a high molecular weight was obtained by optimizing the reaction conditions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 777–793, 1999     

Poly (glycerol‐sebacate) bioelastomers: 2. Synthesis using Brabender Plasticoder® as a batch reactor

Poly (glycerol‐sebacate) polymers are seen as useful materials for biomedical applications. In this article, poly (glycerol‐sebacate) oligomers were synthesized by modifying a Brabender Plasticorder^® as a batch reactor. The samples collected over a reaction period of 5 h were characterized using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The number‐average molecular weight (M_n) and weight‐average molecular weight (M_w) of the oligoesters were determined using matrix‐assisted laser desorption/ionization time‐of‐flight spectroscopy (MALDI‐TOF). The polydispersity indices of these oligoesters produced were within bounds of current commercial polymers. The gel‐point of the reaction was determined from the crossover point of the storage and loss moduli, and the reaction rate constant was calculated using the torque data of the rheometer. The kinetic rate constant and the extent of the reaction in the Brabender were higher than the corresponding values obtained from the conventional laboratory reaction process. The challenges and possibilities in scaling up a batch process to a continuous process (e.g., reactive extrusion) are discussed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42852.     

A study on adsorption of poly(methyl methacrylate) on aluminium silicate

Effect of temperature, solvent power, and molecular weight on the adsorption of poly methyl methacrylate (PMMA) on aluminium silicate has been studied. Kinetics of adsorption have been also investigated at 30° and 45 °C. The values of rate constants at these temperatures are 1.4 · 10^?2 and 1.0 · 10^?2 min^?1 respectively. The adsorption data have been analysed according to the Langmuir and the Simha -Frisch -Eirich (SFE) isotherms. The results could be adequately explained in terms of the Langmuir isotherm.