Synthesis of periodic copolymers via ring‐opening copolymerizations of cyclic anhydrides with tetrahydrofuran using nonafluorobutanesulfonimide as an organic catalyst and subsequent transformation to aliphatic polyesters

To synthesize polyesters and periodic copolymers catalyzed by nonafluorobutanesulfonimide (Nf₂NH), we performed ring‐opening copolymerizations of cyclic anhydrides with tetrahydrofuran (THF) at 50–120 °C. At high temperature (100–120 °C), the cyclic anhydrides, such as succinic anhydride (SAn), glutaric anhydride (GAn), phthalic anhydride (PAn), maleic anhydride (MAn), and citraconic anhydride (CAn), copolymerized with THF via ring‐opening to produce polyesters (M_n = 0.8–6.8 × 10³, M_n/M_w = 2.03–3.51). Ether units were temporarily formed during this copolymerization and subsequently, the ether units were transformed into esters by chain transfer reaction, thus giving the corresponding polyester. On the other hand, at low temperature (25–50 °C), ring‐opening copolymerizations of the cyclic anhydrides with THF produced poly(ester‐ether) (M_n = 3.4–12.1 × 10³, M_w/M_n = 1.44–2.10). NMR and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectra revealed that when toluene (4 M) was used as a solvent, GAn reacted with THF (unit ratio: 1:2) to produce periodic copolymers (M_n = 5.9 × 10³, M_w/M_n = 2.10). We have also performed model reactions to delineate the mechanism by which periodic copolymers containing both ester and ether units were transformed into polyesters by raising the reaction temperature to 120 °C. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Dynamic light scattering studies of atactic and syndiotactic poly(methyl methacrylate)s in dilute theta solution

The present article considers the coil‐to‐globule transition behavior of atactic and syndiotactic poly(methyl methacrylates), (PMMA) in their theta solvent, n‐butyl chloride (nBuCl). Changes in Rh in these polymers with temperature in dilute theta solutions were investigated by dynamic light scattering. The hydrodynamic size of atactic PMMA (a‐PMMA‐1) in nBuCl (M_w: 2.55 × 10⁶ g/mol) decreases to 61% of that in the unperturbed state at 13.0°C. Atactic PMMA (a‐PMMA‐2) with higher molecular weight (M_w: 3.3 × 10⁶ g/mol) shows higher contraction in the same theta solvent (α_η = R_h(T)/R_h (θ) = 0.44) at a lower temperature, 7.25°C. Although syndiotactic PMMA (s‐PMMA) has lower molecular weight than that of atactic samples (M_w: 1.2 × 10⁶), a comparable chain collapse was observed (α_η = 0.63) at 9.0°C. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2253–2260, 1999     

Semi‐micro reversed‐phase liquid chromatography for the separation of alkyl benzenes and proteins exploiting methacrylate‐ and polystyrene‐based monolithic columns

Monolithic columns were synthesized inside 1.02 mm internal diameter fused‐silica lined stainless‐steel tubing. Styrene and butyl, hexyl, lauryl, and glycidyl methacrylates were the functional monomers. Ethylene glycol dimethacrylate and divinylbenzene were the crosslinkers. The glycidyl methacrylate polymer was modified with gold nanoparticles and dodecanethiol (C₁₂). The separation of alkylbenzenes was investigated by isocratic elution in 60:40 v/v acetonitrile/water. The columns based on polystyrene‐co‐divinylbenzene and poly(glycidyl methacrylate)‐co‐ethylene glycol dimethacrylate modified with dodecanethiol did not provide any separation of alkyl benzenes. The poly(hexyl methacrylate)‐co‐ethylene glycol dimethacrylate and poly(lauryl methacrylate)‐co‐ethylene glycol dimethacrylate columns separated the alkyl benzenes with plate heights between 30 and 60 μm (50 μL min^?1 and 60°C). Similar efficiency was achieved in the poly(butyl methacrylate)‐co‐ethylene glycol dimethacrylate column, but only at 10 μL min^?1 (0.22 mm s^?1). Backpressures varied from 0.38 MPa in the hexyl methacrylate to 13.4 MPa in lauryl methacrylate columns (50 μL min^?1 and 60°C). Separation of proteins was achieved in all columns with different efficiencies. At 100 μL min^?1 and 60°C, the lauryl methacrylate columns provided the best separation, but their low permeability prevented high flow rates. Flow rates up to 500 μL min^?1 were possible in the styrene, butyl and hexyl methacrylate columns.     

Synthesis and polymerization of N‐(4‐tetrahydropyranyl‐oxyphenyl)maleimide

N‐(4‐Tetrahydropyranyl‐oxy‐phenyl)maleimide (THPMI) was prepared and polymerized by radical or anionic initiators. THPMI could be polymerized by 2,2′‐azobis(isobutyronitrile) (AIBN) and potassium tert‐butoxide. Radical polymers (poly(THPMI)r) were obtained in 15–50% yields for AIBN in THF at 65°C after 2–5 h. The yield of anionic polymers (poly(THPMI)a) obtained from potassium tert‐butoxide in THF at 0°C after 20 h was 91%. The molecular weights of poly(THPMI)r and poly(THPMI)a were M_n = 2750–3300 (M_w/M_n = 1.2–3.3) and M_n = 11300 (M_w/M_n = 6.0), respectively. The difference in molecular weights of the polymers was due to the differences in the termination mechanism of polymerization and the solubility of these polymers in THF. The thermal decomposition temperatures were 205 and 365°C. The first decomposition step was based on elimination of the tetrahydropyranyl group from the poly(THPMI). Positive image patterns were obtained by chemical amplification of positive photoresist composed of poly(THPMI) and 4‐morpholinophenyl diazonium trifluoromethanesulfonate used as an acid generator. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 341–347, 1999     

Polymerization of 1-octene and determination of markhouwink constants of poly(1-octene)

The polymerization of 1-octene initiated by methylalumoxane（MAO）-activated Ni（Ⅱ）-based-α-diimine complexes[（2,6-i-Pr）₂C₆H₃-DAB（An）]NiBr₂ was investigated.Using this catalyst,poly（1-octene）s with molecular weight between 100×10³ and 400×10³ and polydispersity（M_w/M_n） between 1.3 and 1.5 were synthesized successfully by varying reaction time at room temperature.The poly（1-octene）s were amorphous polymers and could be well soluble in tetrahydrofuran（THF）.After fractional precipitation,poly（1-octene）s with narrow molecular weight distributions（M_w/M_n≤1.12） were obtained.Their weight-average molecular weights were measured by gel permeation chromatography（GPC） in conjunction with online model BI-MwA multiangle laser light scattering（MALLS）,and their intrinsic viscosities were measured by Maron’s single-point method.The k and a values in Mark-Houwink equation[η]= KM^αin THF at 40℃were 0.089 mL/g and 0.61 respectively.     

Polymerization of MMA catalyzed by different novel mixed ligand lanthanocene{(Cp)(Cl) LnSchiff-base (THF)},(COT) -Ln(methoxyethylindenyl)(THF) /Al (i -Bu)_3 systems

This article deals that the rare earth metal complexes along with Al(i'-Bu),can catalyze the polymerization of methyl-methacrylate (MMA) into high molecular weight poly(MMA) along with narrow molecular weight distributions (MWD).A typical example was mentioned in the case of {Cp(Cl) Sm-Schiff-base(THF)} which expresses maximum (conv.% = 55.46 and Mn=354×103) efficiency along with narrow MWD (Mw/Mn<2) at 60℃.The resulting polymer was partially syndiotactic (>60%).The effect of the catalyst,temperature,catalyst/MMA molar ratio,catalyst/Al( i-Bu)3 molar ratio on the polymerization of MMA at 60℃ were also investigated.     

Rotational diffusion of 9,10-diphenylanthracene in di-n-butyl phthalate solutions of polystyrenes by the fluorescence polarization method: Dependence on polymer concentration and molecular weight

A versatile double-beam polarization fluorimeter has been constructed for measuring the polarization of fluorescence from polymer solutions, melts, and glasses. Polarizations can be determined over a range of temperatures from ?20 to +80°C in a controlled atmosphere with a precision of ±0.001 to ±0.005 for the studies reported herein. Data collected at different temperatures for 1.5 × 10^?5M solutions of 9,10-diphenylanthracene (PA) in di-n-butyl phthalate (BP) fit a relation of the Perrin type, 1/P = (1/P₀) + (ST/_η1), where P is the polarization, T is the absolute temperature, and _η1 is the solvent viscosity. The constants P₀ and S were 0.400 ± 0.005 and (7.4 ± 0.3) × 10^?3 P/°K, respectively. Polarizations were also determined at 25.0 ± 0.1°C for BP solutions containing 1.5 × 10^?5M PA and polystyrenes at various weight fractions w₂ and molecular weights M. Rotational friction coefficients ζ_r deduced from these data showed no dependence on M from 5.1 × 10⁴ to 8.6 × 10⁵ g/mole, and a gradual increase as w₂ was varied from 0 to 0.1. It is concluded from these results that PA is an especially attractive emitter for rotational diffusion studies in nonaqueous systems, and that the abrupt changes in ζ_r with w₂ and M observed for some other emitter–polymer systems and attributed to onset of coil overlap are not universal characteristics of such systems.     

Synthesis and characterization of biocompatible poly (L-lactide) using zinc (II) salen complex

Abstract

A biocompatible zinc (II) complex based on a tetradentate N,N,O,O-type salen ligand was synthesized, characterized and used for the solvent-free ring-opening polymerization (ROP) of L-lactide in bulk at 180?°C to prepare high molecular weight poly(L-lactide) (M_n : 82,600?Da; M_w : 140,000?Da; PDI: 1.70). Poly(L-lactide) (PLLA) was characterized using FTIR, ¹H NMR, ¹³C NMR, GPC, TGA, DSC, WAXD, and MALDI-ToF. Kinetic measurement was carried out and first-order behavior to monomer was observed. The k _app was found as 6?±?0.001?×?10^?4?s^?1. The biocompatibility of the PLLA was confirmed by in vitro cytotoxicity against NIH/3T3 fibroblast cell line and can be used in biomedical applications.     

Degradation of poly(acrylates) under SF5+ primary ion bombardment studied using time‐of‐flight secondary ion mass spectrometry. 2. Poly(n‐alkyl methacrylates)

Polyatomic primary ions offer low penetration depth and high damage removal rates in some polymers, facilitating their use in the molecular depth profiling of these polymers by secondary ion mass spectrometry (SIMS). This study is the second in a series of systematic characterizations of the effect of polymer chemistry on degradation under polyatomic primary ion bombardment. In this study, time‐of‐flight SIMS (ToF‐SIMS) was used to measure the damage of ～90 nm thick spin‐cast poly(methyl methacrylate), poly(n‐butyl methacrylate), poly(n‐octyl methacrylate) and poly(n‐dodecyl methacrylate) films under extended (～2 × 10¹⁴ ions cm^?2) 5 keV SF₅⁺ bombardment. The degradation of the poly(n‐alkyl methacrylates) were compared to determine the effect of the length of the alkyl pendant group on their degradation under SF₅⁺ bombardment. The sputter rate and stability of the characteristic secondary ion intensities of these polymers decreased linearly with alkyl pendant group length, suggesting that lengthening the n‐alkyl pendant group resulted in increased loss of the alkyl pendant groups and intra‐ or intermolecular cross‐linking under SF₅⁺ bombardment. These results are partially at variance with the literature on the thermal degradation of these polymers, which suggested that these polymers degrade primarily via depolymerization with minimal intra‐ or intermolecular cross‐linking. Copyright © 2004 John Wiley & Sons, Ltd.     

Thermal Decomposition and Glass Transition Temperature of Poly(phenyl Methacrylate) and Poly(cyclohexyl Methacrylate)

The thermal decomposition and the glass transition temperature T_g of poly(phenyl methacrylate) (PPhMA) and poly(cyclohexyl methacrylate) (PcHU) were studied with a differential scanning calorimeter (DSC). The undecomposed and decomposed polymers were analyzed by gel permeation chromatography (GPC) for molecular weight distributions and by DSC for changes in the thermal properties, e.g., T_g. For all values of weight-loss α, the thermal stability of the polymers follows the order: Poly-(methyl methacrylate) (PMMA) = PcHMA > poly(ethyl methacrylate) (PEMA) > PPhMA > poly(n-butyl methacrylate) (PnBuMA) > poly(isobutyl methacrylate) (PiBuMA). In the depolymerization reactions that occur during the isothermal decomposition of PPhMA, there is no specific preference for longer or shorter chains although a minor fraction of the volatilized fraction with an [Mbar]_w 10^?5 of 2.5 and an [Mbar] _n |MX 10.^?5 of 1.5 does undergo chain recombination yielding high molecular weight products with an M_w × 10^?6 of 1.35 and an M_n × 10^?6 of 1.0 to 1.23. In the case of PcHMA, depolymerizations did show a preference for longer chains. No chain recombination, however, was found to take place. Activation energy of decomposition for substituted poly-methacrylates follows the order: PnBuMA = PiBuMA >; PEMA >; PcHMA >; PMMA >; PPhMA. T_{g e} values of PPhMA samples varied from 362 K for undecomposed polymers to 396 K for a polymer treated at 300° C. The literature value of 383 K does fall within this range. In the case of PcHMA, an average T_ge of 356 f 6.0 ± is not far removed from the reported value of 359 K.     

Degradation of poly(acrylates) under SF5+ primary ion bombardment studied using time‐of‐flight secondary ion mass spectrometry. 3. Poly(hydroxyethyl methacrylate) with chemical derivatization

Molecular depth profiling of polymers by secondary ion mass spectrometry (SIMS) has focused on the use of polyatomic primary ions due to their low penetration depth and high damage removal rates in some polymers. This study is the third in a series of systematic characterizations of the effect of polymer chemistry on degradation under polyatomic primary ion bombardment. In this study, time‐of‐flight SIMS (ToF‐SIMS) was used to assess 5 keV SF₅⁺‐induced damage of ～90 nm thick spin‐cast poly(2‐hydroxyethyl methacrylate) (PHEMA) and ～130 nm thick trifluoroacetic anhydride‐derivatized PHEMA (TFAA‐PHEMA) films. The degradation of these polymers under extended SF₅⁺ bombardment (～2 × 10¹⁴ ions cm^?2) was compared to determine the effect of the pendant group chemistry on their degradation. The sputter rate and ion‐induced damage accumulation rate of PHEMA were similar to a poly(n‐alkyl methacrylate) of similar pendant group length, suggesting that the addition of a terminal hydroxyl group to the alkyl pendant group does not markedly change the stability of poly(n‐alkyl methacrylates) under SF₅⁺ bombardment. The sputter rate and ion‐induced damage accumulation rate of TFAA‐PHEMA were much higher than a poly(n‐alkyl methacrylate) of similar pendant group length, suggesting that derivatization of the terminal hydroxyl group can significantly reduce degradation of the polymer under SF₅⁺ bombardment. This result is in good agreement with the literature on the thermal and radiation‐induced degradation of fluorinated poly(alkyl methacrylates), which suggests that the electron‐withdrawing fluorinated pendant group increases the probability of depolymerization. Copyright © 2004 John Wiley & Sons, Ltd.     

Ring-Opening Polymerization of Cyclic Monomers with Aluminum Triflate

A green method for the controlled synthesis of aliphatic polymers is presented. The ring-opening polymerizations of cyclic monomers including several lactones, such as caprolactone (CL) or pentadecalactone (PDL), and cyclic anhydride monomers, such as succinic anhydride (SUC) and tetrahydrofuran (THF), catalyzed by a series of metal triflates (trifluoromethanesulfonate) were studied. Aluminum triflate was found to be an advantageous candidate to catalyze the ring-opening polymerization of cyclic monomers. The details of the ring-opening polymerization of CL catalyzed by aluminum triflate were studied. The maximum number average molecular weight (M_n), polydispersity (M_w/M_n) and yield of the obtained poly(-caprolactone) (PCL) at 60 °C for 6 hours were 18,400, 1.94 and 89 wt%, respectively. Those of poly(pentadecalactone) (PPDL) at 100 °C for 6 hours were 12,400, 2.24 and 49 wt%, respectively. The M_n, M_w/M_n and yield of the obtained poly(butylene succinate) (PBS) from SUC and THF at 100 °C for 48 hours were 4,900, 2.03 and 84 wt%, respectively. Furthermore, the mechanism of the polymerization was discussed based on the relationship between the conversion of CL and time. The molecular weight buildup of PCL was linear with a conversion in 50 min before the conversion reached 100 % and with M_w/M_n stabilized at about 1.5. The M_w/M_n of PCL then gradually increased. From these data, a living polymerization with a small transesterification was suggested from the PCL polymerization by aluminum triflate.     

Properties and chain flexibility of poly(tetrahydro-4H-pyranyl-2-methacrylate)

The dilute-solution properties of six poly(tetrahydro-4H-pyranyl-2-methacrylate) (PTHPM) fractions covering the molecular weight (M _w) range 4.8 × 10⁴ to 8.4 × 10⁵ (M _w/M _n = 1.2–1.4) were studied in tetrahydrofuran, a good solvent, and in isobutanol, a θ solvent a t 30.5°C as determined by light scattering from the A₂ vs. T plot. The unperturbed dimensions were calculated from a low-angle laser light-scattering and intrinsic-viscosity data. The results indicate that PTHPM is less extended chain than poly(cyclohexyl methacrylate) (PCyM). The higher flexibility of PTHPM parallels the lower T, (57°C) of this polymer relative to PCyM (66°C).     

AUTOCATALYTIC REDUCTION OF PYRIDINECOBALOXIME(III) BY MOLECULAR HYDROGEN

Abstract

In the presence of added cobaloxime(II), hydroxopyridinecobaloxime(III) is autocatalytically reduced by molecular hydrogen in methanol at 20°C. The sigma-shaped volumetric curves were evaluated by computer simulation of the system of differential equations corresponding to a 4-step mechanism. The key reduction step is presumably H-atom transfer from hydridocobaloxime(III) to cobaloxime(III). The lower limit of its rate constant is k₄=(5.0 ± 0.5) × 10⁴ M^?1 sec^?1 at 20°C. Hydridopyridinecobaloxime(III) is thermodynamically unstable, its estimated formation equilibrium constant being (3.9 ± 0.6) × 10^?4 M^?1. The possible role of cobaloxime(I) species is discussed.     

Anionic Polymerization Behavior of α-Methylene-N-methylpyrrolidone

Anionic polymerization of α-methylene-N-methylpyrrolidone ( MMP ) was carried out in THF at −78∼0 °C with diphenylmethylpotassium (Ph₂CHK) and with diphenylmethyllithium (Ph₂CHLi) in the presence of Lewis acidic diethylzinc (Et₂Zn). Poly( MMP )s possessing predicted molecular weights based on the molar ratios between monomer and initiators and narrow molecular weight distributions (M_w/M_n < 1.1) were obtained in quantitative yields. It was demonstrated that the propagating chain end of poly( MMP ) was stable at −30 °C to form the polymers with well-defined chain structures. From the polymerizations at the various temperatures ranging from −50 to −30 °C, the apparent rate constant and the activation energy of the polymerization were estimated as follows: ln k = −6.93 × 10³/T + 25.7 and 57 ± 5 kJ mol⁻¹, respectively.     

Synthesis and Characterization of Styrene-Isoprene Diblock Copolymers

A simple reusable apparatus for the synthesis of up to 40 g quantities of poly(styrene-b-isoprene) diblock copolymers of reasonably low (1.2 to 1.5) polydispersity has been described. The diblock copolymers synthesized were characterized by gel permeation chromatography (GPC), membrane osmometry, viscosimetry, and nuclear magnetic resonance (NMR) spectroscopy. Number-average molecular weights (M _n) calculated from the raw GPC chromatographs of the diblock copolymers using the summation method and M versus elution volume plots for polystyrene and polyisoprene standards agree well with those measured experimentally with osmometry. It is suggested that for polydisperse block copolymers this method is simpler than the use of a universal calibration curve. Mark-Houwink constants K ans a for polyisoprene having 18% (1,2-), 66% (3,4-), and 16% (1,4-) microstructure were found to be 3.2 × 10^?4 dL/g and 0.67, respectively, in THF at 25°C. In toluene at 30°C, K = 2.0 × 10^?4 dL/g and α = 0.7 were obtained. The diblock copolymers had 26% (1,2-), 60% (3,4-), and 14% (1,4-) microstructure in the isoprene segments, and the values of K and a for these copolymers (PS > 50%, M 20.0 × 10³) in THF at 25°C were 9.0 × 10^?5 dL/g and 0.75. For M < 20.0 × 10³ the value of α was 0.5. The experimental values of [η] were found to be lower than those calculated theoretically, presumably due to the polydisperse nature and the biellipsoidal configuration of the diblock copolymers.     

Thermal and ion transport properties of hydrophilic and hydrophobic polymerized styrenic imidazolium ionic liquids

Polymerized ionic liquids (PILs) are a platform for fundamental studies of structure‐property relationships in single ion conductors, with potential applications in energy storage and conversion. The synthesis, thermal properties, and ionic conductivities of homologous, narrow dispersity styrenic PILs are described. Hydrophilic poly(4‐vinylbenzyl alkylimidazolium chloride) (PVBn(alkyl)ImCl) homopolymers with constant average degrees of polymerization were synthesized by post‐synthetic functionalization of a poly(4‐vinylbenzyl chloride) (M_n = 15.9 kg/mol, M_w/M_n = 1.34) master batch with N‐alkylimidazoles (alkyl = ? CH₃ (Me), ? C₄H₉ (Bu), and ? C₆H₁₃ (Hex)). The chloride counterions of PVBnHexImCl were exhaustively metathesized with BF, PF, and bis(trifluoromethanesulfonyl)imide (TFSI^?) to yield a series of hydrophobic PILs. Thermogravimetric analyses indicate that PVBn(alkyl)ImCl homopolymers are unstable above 220 °C, whereas the hydrophobic PILs remain stable up to 290 °C. The glass transition temperatures (T_g) decrease with both increasing alkyl side‐chain length and increasing counterion size, exemplified by T_g = 9 °C for PVBnHexImTFSI. Hydrophilic PILs exhibit high ionic conductivities (as high as ～0.10 S cm^?1) that depend on the relative humidity, water uptake, and the PIL side chain length. The hydrophobic PILs exhibit lower conductivities (up to ～5 × 10^?4 S cm^?1) that depend predominantly on the polymer T_g, however, counterion size and symmetry also contribute. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1287–1296, 2011     

Molecular chain properties of poly (N-isopropyl acrylamide)

A series of poly( N-isopropyl acrylamide) (PNIPAM) samples with molecular weight ranging from 2.23×10~4 to 130×10~4 and molecular weight distribution M_w/M_n≤1.28 were obtained by free radical polymerization and repeat precipitation fractionation. The molecular weight M_w, second virial coefficient A_2 as well as the mean-square-root radius of gyration 〈S~2〉 for PNIPAM samples in tetrahydrofuran (THF) were determined by light scattering, and the relations were estimated at A_2 ∞ M_w~0.25) and 〈S~2〉~(1/2)=1.56×10~(-9) M_w~(0.56). The intrinsic viscosity for THF solution and methanol solution of PNIPAM samples was measured and the Mark-Houwink equations were obtained as [η]=6.90×10~(-5) M~(0/73) (THF solution) and [η]=1.07×10~(-4) M~(0.71) (methanol solution). The above results indicate that both THF and methanol are good solvents for PNIPAM. The limit characteristic ratio C_∞ for PNIPAM in the two solutions was determined to be 10.6 by using Kurata-Stockmayer equation, indicating that the f     

Synthesis of poly(p‐phenylene) macromonomers and multiblock copolymers

Rigid‐rod poly(4′‐methyl‐2,5‐benzophenone) macromonomers were synthesized by Ni(0) catalytic coupling of 2,5‐dichloro‐4′‐methylbenzophenone and end‐capping agent 4‐chloro‐4′‐fluorobenzophenone. The macromonomers produced were labile to nucleophilic aromatic substitution. The molecular weight of poly(4′‐methyl‐2,5‐benzophenone) was controlled by varying the amount of the end‐capping agent in the reaction mixture. Glass‐transition temperatures of the macromonomers increased with increasing molecular weight and ranged from 117 to 213 °C. Substitution of the macromonomer end groups was determined to be nearly quantitative by ¹H NMR and gel permeation chromatography. The polymerization of a poly(4′‐methyl‐2,5‐benzophenone) macromonomer [number‐average molecular weight (M_n) = 1.90 × 10³ g/mol; polydispersity (M_w)/M_n = 2.04] with hydroxy end‐capped bisphenol A polyaryletherketone (M_n = 4.50 × 10³ g/mol; M_w/M_n = 1.92) afforded an alternating multiblock copolymer (M_n = 1.95 × 10⁴ g/mol; M_w/M_n = 6.02) that formed flexible, transparent films that could be creased without cracking. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3505–3512, 2001     

Scission Efficiencies of Short Chain Branches in the γ-Radiolysis of Ethylene-α-Olefin Copolymers

Abstract

γ-Irradiation of copolymers of ethylene with propene, 1-butene, and 1-hexene, containing from 1 to 6 alkyl short chain branches per 1000 carbon atoms, at 25°C in vacuum, produced small amounts of n-alkanes with a maximum yield for the alkane corresponding to the alkyl branch of the α-olefin unit. A multilinear regression analysis showed a highly significant dependence of G(C_n alkane) on the frequency of alkyl branches containing n carbon atoms, determined by ¹³C-NMR. The corrections to the G(C_n alkane) yields from other fragmentation processes were substantial but no dependence for G(C_n alkane) on fragmentation of chain ends or fragmentation of the chain following branch elimination could be deduced from the data. The scission efficiencies = G(alkane) divided by the branch frequency per 1000 carbon atoms ± 95% confidence limits were (0.7 ± 0.7) × 10^?3, (2.7 ± 0.8) × 10^?3, and (1.5 ± 0.3) × 10^?3, for methyl, ethyl, and butyl branches, respectively. These factors can be used to determine the short-chain branch frequencies in similar polymers from n-alkane yields on γ-irradiation.