The role of the ratio (PEG:PPG) of a triblock copolymer (PPG‐b‐PEG‐b‐PPG) in the cure kinetics,miscibility and thermal and mechanical properties in an epoxy matrix

The aim of this study was to evaluate the role of different poly(ethylene glycol):poly(propylene glycol) (PEG:PPG) molar ratios in a triblock copolymer in the cure kinetics, miscibility and thermal and mechanical properties in an epoxy matrix. The poly(propylene glycol)‐block‐poly(ethylene glycol)‐block‐poly(propylene glycol) (PPG‐b‐PEG‐b‐PPG) triblock copolymers used had two different molecular masses: 3300 and 2000 g mol^?1. The mass concentration of PEG in the copolymer structure played a key role in the miscibility and cure kinetics of the blend as well as in the thermal–mechanical properties. Phase separation was observed only for blends formed with the 3300 g mol^?1 triblock copolymer at 20 wt%. Concerning thermal properties, the miscibility of the copolymer in the epoxy matrix reduced the T_g value by 13 °C, although a 62% increase in fracture toughness (K_IC) was observed. After the addition of PPG‐b‐PEG‐b‐PPG with 3300 g mol^?1 there was a reduction in the modulus of elasticity by 8% compared to the neat matrix; no significant changes were observed in T_g values for the immiscible system. The use of PPG‐b‐PEG‐b‐PPG with 2000 g mol^?1 reduced the modulus of elasticity by approximately 47% and increased toughness (K_IC) up to 43%. Finally, for the curing kinetics of all materials, the incorporation of the triblock copolymer PPG‐b‐PEG‐b‐PPG delayed the cure reaction of the DGEBA/DDM (DGEBA, diglycidyl ether of bisphenol A; DDM, Q3‐4,4′‐Diaminodiphenylmethane) system when there is miscibility and accelerated the cure reaction when it is immiscible. All experimental curing reactions could be fitted to the Kamal autocatalytic model presenting an excellent agreement with experimental data. This model was able to capture some interesting features of the addition of triblock copolymers in an epoxy resin. © 2018 Society of Chemical Industry     

Effect of annealing time and molecular weight on melt memory of random ethylene 1‐butene copolymers

The effects of annealing time and molecular weight on the strong melt memory effect observed in random ethylene 1‐alkene copolymers are analyzed in a series of model ethylene 1‐butene copolymers with 2.2 mol% branches. Melt memory is associated with molten clusters of ethylene sequences from the initial crystals that remain in close proximity and are unable to diffuse quickly to the randomized melt state, thus increasing the recrystallization rate. Melt memory persists even for greater than 1000 min annealing indicating a long‐lived nature of the clusters that only fully dissolve at melt temperatures above a critical value (>160 °C). Below the critical melt temperature, molecular weight and annealing temperature have a strong influence on the slow kinetics of melt memory. For the copolymers analyzed, slow dissolution of clusters is experimentally observed only for M_w < 50 000 g mol^?1. More stable clusters that survive higher annealing temperatures display slower dissolution rates than clusters remaining at lower temperatures. The threshold crystallinity level to enable melt memory (X_c,threshold) decreases with increasing molecular weight and decreasing annealing temperature similarly to the variation of the chain diffusivity in the melt. The process leading to melt memory is thermally activated as the variation of X_c,threshold with temperature follows Arrhenius behavior with high activation energy (ca 108 kJ mol^?1) that is independent of molecular weight. © 2018 Society of Chemical Industry     

Synthesis and characterization of oligosalicylaldehyde‐graft‐oligoaniline and its beginning oligomers

Conjuge bonding oligosalicylaldehyde‐graft‐oligoaniline (OSA‐graft‐OA) was synthesized from the polycondensation reaction of oligosalicylaldehyde (OSA) with oligoaniline (OA). There were various functional groups such as ? OH, ? NH and ? CH?N in the structure of the graft cooligomer. The physical properties of graft‐co‐oligomers such as melting temperature and solubility were studied: number‐average molecular weight, mass‐average molecular weight, and a polydispersity index of OA, OSA, and fractions of the graft cooligomers [(OSA‐graft‐OA)‐I] and [(OSA‐graft‐OA)‐II] were found to be 740, 780 g mol^?1,1.05; 3700, 5990 g mol^?1, 1.62; 990, 2770 g mol^?1, 2.80 and 1300, 4100 g mol^?1, 3.15, respectively. The FTIR and UV‐Vis spectra of the graft cooligomer were compared with those of beginning oligomers. The spectral analyses results showed that the OSA‐graft‐OA synthesized from the polycondensation reaction of aromatic amine with aldehyde that have long oligophenol macromolecule bonded each other with an azomethine bridge through oligophenylamine side chains. The thermal stability of the graft cooligomer and oligomers were measured by thermogravimetric analysis (TG) under an air atmosphere. According to TG analyses, the carboneous residues of the [(OSA‐graft‐OA)‐I) (soluble in ethanol) and (OSA‐graft‐OA)‐II) (soluble in toluene)] were 23 and 40%, respectively, at 1000°C. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 218–226, 2002     

Synthesis and biological activity of phthalimide‐based polymers containing 5‐fluorouracil

The attachment of anticancer agents to polymers is a promising approach towards reducing the toxic side‐effects and retaining the potent antitumour activity of these agents. A new tetrahydrophthalimido monomer containing 5‐fluorouracil (ETPFU) and its homopolymer and copolymers with acrylic acid (AA) and with vinyl acetate (VAc) have been synthesized and spectroscopically characterized. The ETPFU contents in poly(ETPFU‐co‐AA) and poly(ETPFU‐co‐VAc) obtained by elemental analysis were 21 mol% and 20 mol%, respectively. The average molecular weights of the polymers determined by gel permeation chromatography were as follows: M_n = 8900 g mol^?1, M_w = 13 300 g mol^?1, M_w/M_n = 1.5 for poly(ETPFU); M_n = 13 500 g mol^?1, M_w = 16 600 g mol^?1, M_w/M_n = 1.2 for poly(ETPFU‐co‐AA); M_n = 8300 g mol^?1, M_w = 11 600 g mol^?1, M_w/M_n = 1.4 poly(ETPFU‐co‐VAc). The in vitro cytotoxicity of the compounds against FM3A and U937 cancer cell lines increased in the following order: ETPFU > 5‐FU > poly(ETPFU) > poly(ETPFU‐co‐AA) > poly(ETPFU‐co‐VAc). The in vivo antitumour activities of all the polymers in Balb/C mice bearing the sarcoma 180 tumour cell line were greater than those of 5‐FU and monomer at the highest dose (800 mg kg^?1). © 2002 Society of Chemical Industry     

Examining the preparation and characterization of coatings based on linear aromatic terpoly(methoxy‐cyanurate‐thiocyanurate)s

Two series of terpoly(methoxy‐cyanurate‐thiocyanurate)s based on thiodiphenol and dithiodiphenyl sulfide and on dihydroxydiphenyl ether and dithiodiphenyl ether, were prepared in good yield and purity and fully characterized. Most of the resulting polymers, formed at room temperature using phase transfer catalysis, can be cast into films with good resilience and thermal stability (some examples suffer practically no mass loss when held isothermally at 190 °C and only display appreciable losses when held continuously at 225 °C). Char yields of 53%?61% are achieved in nitrogen depending on backbone structure. Some problems were encountered with solubility, particularly with copolymers, which limited molecular weight analysis, but values of M_n = 8000–13 000 g mol^?1 were obtained for the polymers based on thiodiphenol and dithiodiphenyl sulfide, and M_n = 5000–13 000 g mol^?1 for the polymers based on dihydroxydiphenyl ether and dithiodiphenyl ether. DSC reveals polymerization exotherms with maxima at 184–207 °C (ΔH_p = 43–59 kJ mol^?1), which are believed to be due to isomerization of the cyanurate to the isocyanurate (activation energies span 159–195 kJ mol^?1). Molecular simulation shows that diphenylether and diphenylsulfide display very similar conformational energy surfaces and would therefore be expected to adopt similar conformations, but the diphenylsulfide offers less resistance to deformations that increase the proximity of the two phenyl rings and results in more resilient films. © 2013 Society of Chemical Industry     

Time‐resolved small‐angle X‐ray scattering study of void fraction evolution in high‐density polyethylene during stress unloading and strain recovery

By means of time‐resolved small‐angle X‐ray scattering, we developed an analysis methodology to assess the void volume fraction ?_v in high‐density polyethylene (HDPE) during tensile testing. The specimens were first drawn up to different imposed strains, and subsequently were subjected to stress unloading and strain recovery stages. During the loading stage, ?_v progressively increased with the strain level, starting from a well‐defined onset strain prior to the yield point. In particular, ?_v reached a maximum of 8.75 vol% for a strain of 12.5% in the case of a HDPE grade with a molecular weight of 105 000 g mol^?1. Stress unloading and strain recovery caused a decrease in ?_v attained at the end of the loading stage. For a HDPE grade with a molecular weight of 55 000 g mol^?1, ?_v was more important during the loading stage and the decrease in ?_v was less marked during the stress unloading stage when compared to the HDPE with molecular weight of 105 000 g mol^?1. The residual and reversible components of void volume fraction were revealed. © 2015 Society of Chemical Industry     

Synthesis and biological activity of medium range molecular weight polymers containing exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthalimidocaproic acid

A new monomer, exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthalimidocaproic acid (ETCA), was prepared by reaction of maleimidocaproic acid and furan. The homopolymer of ETCA and its copolymers with acrylic acid (AA) or with vinyl acetate (VAc) were obtained by photopolymerizations using 2,2‐dimethoxy‐2‐phenylacetophenone as an initiator at 25 °C. The synthesized ETCA and its polymers were identified by FTIR, ¹H NMR and ¹³C NMR spectroscopies. The apparent average molecular weights and polydispersity indices determined by gel permeation chromatography (GPC) were as follows: M_n = 9600 g mol^?1, M_w = 9800 g mol^?1, M_w/M_n = 1.1 for poly(ETCA); M_n = 14 300 g mol^?1, M_w = 16 200 g mol^?1, M_w/M_n = 1.2 for poly(ETCA‐co‐AA); M_n = 17 900 g mol^?1, M_w = 18 300 g mol^?1, M_w/M_n = 1.1 for poly(ETCA‐co‐VAc). The in vitro cytotoxicity of the synthesized compounds against mouse mammary carcinoma and human histiocytic lymphoma cancer cell lines decreased in the following order: 5‐fluorouracil (5‐FU) ≥ ETCA > polymers. The in vivo antitumour activity of the polymers against Balb/C mice bearing sarcoma 180 tumour cells was greater than that of 5‐FU at all doses tested. © 2001 Society of Chemical Industry     

Vinyl‐type homo‐ and copolymerization of norbornene catalyzed by bis(phenoxyimine) titanium complex

A ternary catalytic system consisting of a bis(phenoxyimine) titanium complex, triisobutylaluminium and an organoboron compound exhibited high activity in the vinyl‐type homopolymerization of norbornene. The obtained polynorbornene showed a modest molecular weight (M _n ≈ 5 × 10⁴ g mol^?1) and broad molecular weight distribution (polydispersity index ≈ 3.5). A copolymer of norbornene with 1,3‐butadiene was prepared using a binary catalytic system consisting of bis(phenoxyimine) titanium complex and triisobutylaluminium. The norbornene units in the copolymer adopted a vinyl‐type addition structure confirmed using distortionless enhancement by polarization transfer 135 ¹³C NMR microstructure analyses. Polymerization kinetics studies showed that neither monomer feed ratio nor conversion had an effect on the composition of the copolymer backbone which was composed of 55% norbornene units and 45% 1,3‐butadiene units. The essentially constant polymer composition implied an alternating nature of chain propagation. The copolymer exhibited good thermal stability and moderate glass transition temperature (50.9–68.2 °C) with a relatively high molecular weight (M _w = 0.18 × 10–1.31 × 10⁵ g mol^?1), and excellent transparency (maximal transmittance >80%). © 2017 Society of Chemical Industry     

Surface microphase separation in PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films

Well‐defined poly(dimethylsiloxane)‐block‐poly(methyl methacrylate)‐block‐poly(2,2,3,3,4,4,4‐heptafluorobutyl methacrylate) (PDMS‐b‐PMMA‐b‐PHFBMA) triblock copolymers were synthesized via atom transfer radical polymerization (ATRP). Surface microphase separation in the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films was investigated. The microstructure of the block copolymers was investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Surface composition was studied by X‐ray photoelectron spectroscopy (XPS). The chemical composition at the surface was determined by the surface microphase separation in the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films. The increase of the PHFBMA content could strengthen the microphase separation behavior in the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films and reduce their surface tension. Comparison between the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymers and the PDMS‐b‐PHFBMA diblock copolymers showed that the introduction of the PMMA segments promote the fluorine segregation onto the surface and decrease the fluorine content in the copolymers with low surface energy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Microphase separation behavior on the surfaces of poly(dimethylsiloxane)‐block‐poly(2,2,3,3,4,4,4‐heptafluorobutyl methacrylate) diblock copolymer coatings

Microphase separation behavior on the surfaces of poly(dimethylsiloxane)‐block‐poly(2,2,3,3,4,4,4‐heptafluorobutyl methacrylate) (PDMS‐b‐PHFBMA) diblock copolymer coatings was investigated. The PDMS‐b‐PHFBMA diblock copolymers were successfully synthesized via atom transfer radical polymerization (ATRP). The chemical structure of the copolymers was characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy. Surface composition was studied by X‐ray photoelectron spectroscopy. Copolymer microstructure was investigated by atomic force microscopy. The microstructure observations show that well‐organized phase‐separated surfaces consist of hydrophobic domain from PDMS segments and more hydrophobic domain from PHFBMA segments in the copolymers. The increase in the PHFBMA content can strengthen the microphase separation behavior in the PDMS‐b‐PHFBMA diblock copolymers. And the increase in the annealing temperature can also strengthen the microphase separation behavior in the PDMS‐b‐PHFBMA diblock copolymers. Moreover, Flory‐Huggins thermodynamic theory was preliminarily used to explain the microphase separation behavior in the PDMS‐b‐PHFBMA diblock copolymers.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis,characterization, conductivity,band gap,and kinetic of thermal degradation of poly‐4‐[(2‐mercaptophenyl) imino methyl] phenol

The oxidative polycondensation reaction conditions of 4‐[(2‐mercaptophenyl) imino methyl] phenol (2‐MPIMP) were studied in an aqueous acidic medium between 40 and 90°C by using oxidants such as air, H₂O₂, and NaOCl. The structures of the synthesized monomer and polymer were confirmed by FTIR, ¹H NMR, ¹³C NMR, and elemental analysis. The characterization was made by TGA‐DTA, size exclusion chromatography (SEC) and solubility tests. At the optimum reaction conditions, the yield of poly‐4‐[(2‐mercaptophenyl) imino methyl]phenol (P‐2‐MPIMP) was found to be 92% for NaOCl oxidant, 84% for H₂O₂ oxidant 54% for air oxidant. According to the SEC analysis, the number‐average molecular weight (M_n), weight‐average molecular weight (M_w), and polydispersity index values of P‐2‐MPIMP were found to be 1700 g mol^?1, 1900 g mol^?1, and 1.118, using H₂O₂; 3100 g mol^?1, 3400 g mol^?1, and 1.097, using air; and 6750 g mol^?1, 6900 g mol^?1, and 1.022, using NaOCl, respectively. According to TG analysis, the weight losses of 2‐MPIMP and P‐2‐MPIMP were found to be 95.93% and 76.41% at 1000°C, respectively. P‐2‐MPIMP showed higher stability against thermal decomposition. Also, electrical conductivity of the P‐2‐MPIMP was measured, showing that the polymer is a typical semiconductor. The highest occupied molecular orbital, the lowest unoccupied molecular orbital, and the electrochemical energy gaps (E′_g) of 2‐MPIMP and P‐2‐MPIMP were found to be ?6.13, ?6.09; ?2.65, ?2.67; and 3.48, 3.42 eV, respectively. Kinetic and thermodynamic parameters of these compounds investigated by MacCallum‐Tanner and van Krevelen methods. The values of the apparent activation energies of thermal decomposition (E_a), the reaction order (n), pre‐exponential factor (A), the entropy change (ΔS*), enthalpy change (ΔH*), and free energy change (ΔG*) were calculated from the TGA curves of compounds. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synergistic extraction of rare earths(III) from chloride medium with mixtures of 1‐phenyl‐3‐methyl‐4‐benzoyl‐pyrazalone‐5 and di‐(2‐ethylhexyl)‐2‐ethylhexylphosphonate

The synergistic effect of 1‐phenyl‐3‐methyl‐4‐benzoyl‐pyrazalone‐5 (HPMBP, HA) and di‐(2‐ethylhexyl)‐2‐ethylhexylphosphonate (DEHEHP, B) in the extraction of rare earths (RE) from chloride solutions has been investigated. Under the experimental conditions used, there was no detectable extraction when DEHEHP was used as a single extractant while the amount of RE(III) extracted by HPMBP alone was also low. But mixtures of the two extractants at a certain ratio had very high extractability for all the RE(III). For example, the synergistic enhancement coefficient was calculated to be 9.35 for Y³⁺, and taking Yb³⁺ and Y³⁺ as examples, RE³⁺ is extracted as RE(OH)A₂.B. The stoichiometry, extraction constants and thermodynamic functions such as Gibbs free energy change ΔG (?17.06 kJ mol^?1), enthalpy change ΔH (?35.08 kJ mol^?1) and entropy change ΔS (?60.47 J K^?1 mol^?1) for Y³⁺ at 298 K were determined. The separation factors (SF) for adjacent pairs of rare earths were calculated. Studies show that the binary extraction system not only enhances the extraction efficiency of RE(III) but also improves the selectivity, especially between La(III) and the other rare earth elements. Copyright © 2006 Society of Chemical Industry     

Effects of molecular weight on dual light‐ and thermo‐responsive behaviors of homopolymers with azobenzene units and terminal oligo(ethylene glycol) units

A series of water‐soluble dual light‐ and thermo‐responsive homopolymers bearing azobenzene units and terminal oligo(ethylene glycol) units with well‐defined molecular weight (M _n = 0.69 × 10⁴ to 4.60 × 10⁴ g mol^?1) were synthesized via reversible addition–fragmentation chain transfer polymerization. All the homopolymers exhibited reversible photoisomerization and their lower critical solution temperatures showed an unusual increase with increasing molecular weight. Interestingly, by increasing the molecular weight, the aggregate morphology of these polymers was found to evolve from a spherical to a cylindrical shape. © 2017 Society of Chemical Industry     

Toughening of cyanate ester resin by N‐phenylmaleimide–N‐(p‐hydroxy)phenyl‐maleimide–styrene terpolymers and their hybrid modifiers

N‐Phenylmaleimide–N‐(p‐hydroxy)phenylmaleimide–styrene terpolymer (HPMS), carrying reactive p‐hydroxyphenyl groups, was prepared and used to improve the toughness of cyanate ester resins. Hybrid modifiers composed of N‐phenylmaleimide–styrene copolymer (PMS) and HPMS were also examined for further improvement in toughness. Balanced properties of the modified resins were obtained by using the hybrid modifiers. The morphology of the modified resins depends on HPMS structure, molecular weight and content, and hybrid modifier compositions. The most effective modification of the cyanate ester resin was attained because of the co‐continuous phase structure of the modified resin. Inclusion of the modifier composed of 10 wt% PMS (M_w 136 000 g mol^?1) and 2.5 wt% HPMS (hydroxyphenyl unit 3 mol%, M_w 15 500 g mol^?1) led to 135% increase in the fracture toughness (K_IC) for the modified resin with a slight loss of flexural strength and retention of flexural modulus and glass transition temperature, compared with the values for the unmodified resin. Furthermore, the effect of the curing conditions on the mechanical and thermal properties of the modified resins was examined. The toughening mechanism is discussed in terms of the morphological and dynamic viscoelastic behaviour of the modified cyanate ester resin system. © 2001 Society of Chemical Industry     

Syntheses and adsorption properties for Hg2+ of chelating resin of crosslinked polystyrene‐supported 2,5‐dimercapto‐1,3,4‐thiodiazole

A novel chelating resin with functional group containing S and N atoms was prepared using chloromethylated polystyrene and 2,5‐dimercapto‐1,3,4‐thiodiazole (also called bismuththiol I, BMT) as materials. Its structure was characterized by infrared spectra and elementary analysis. The results showed that the content of the functional group was 2.07 mmol BMT g^?1 resin, 47% of which were in the form of monosubstitution (PS‐BMT‐1) and 53% in the form of double substitution (PS‐BMT‐2). The adsorption for mercury ion was investigated. The adsorption dynamics showed that the adsorption was controlled by liquid film diffusion. Increasing the temperature was beneficial to adsorption. The Langmuir model was much better than the Freundlich model to describe the isothermal process. The adsorption activation energy (E_a), ΔG, ΔH, and ΔS values calculated were 18.56 kJ·mol^?1, ‐5.99 kJ·mol^?1, 16.38 kJ·mol^?1, and 37.36, J·mol^?1·K^?1, respectively. The chelating resin could be easily regenerated by 2% thiourea in 0.1 mol·L^?1 HCl with higher effectiveness. Five adsorption–desorption cycles demonstrated that this resin was suitable for repeated use without considerable change in adsorption capacity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1646–1652, 2004     

High temperature surface neutralization process with random copolymers for block copolymer self‐assembly

Hydroxyl terminated poly(styrene‐r ‐methyl methacrylate) (P(S‐r ‐MMA )) random copolymers (RCPs ), with molecular weight (M _n) spanning from 1700 to 69 000 g mol^?1 and equal styrene unit content, were grafted at different temperatures onto a silicon oxide surface and subsequently used to study the orientation of nanodomains with respect to the substrate, in cylinder forming polystyrene‐b ‐poly(methyl methacrylate) (PS ‐b ‐PMMA ) block copolymer thin films. When the grafting temperature increases from 250 to 310 °C, a substantial increase in the grafting rate is observed. In addition, an increase in the surface neutralization efficiency occurs thus resulting in an increase in the robustness of the surface neutralization step. These data revealed that the neutralization of the substrate is the result of a complex interplay between RCP film characteristics and underlying substrate properties that can be finely tuned by properly adjusting the temperature of the grafting process. © 2016 Society of Chemical Industry     

Oxo‐biodegradability of high‐density polyethylene films containing limited amount of isotactic polypropylene

Limited amount of isotactic polypropylene (iPP) is added to high‐density polyethylene (HDPE) containing 1% w/w an oxo‐biodegradable additive and extruded and converted to films. The films are put under UV irradiation for different periods of time. Irradiation of the films for 6 weeks imposes remarkable effects on viscosity average molecular weight (M_v) and carbonyl index (CI) of them. M_v decreases from 3.4 × 10⁵ to 4.7 × 10⁴ g mol^?1 for neat HDPE films; from 3.1 × 10⁵ to 3.3 × 10⁴ g mol^?1 for the films containing oxo compound, and from 1.5 × 10⁵ to 2.6 × 10⁴ g mol^?1 for the films containing oxo compound and 1% w/w iPP. Carbonyl index of the neat HDPE films increases from 4 to 8.7 while for the sample containing only the oxo compound it increases from 4.5 to 7.3 and for the sample containing both oxo compound and iPP it decreases from 12.0 to 8.8. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) indicate more cracks and uniform degradation in the samples containing iPP and oxo compound. Thermogravimetric analysis (TGA/DTG) of the samples shows that the samples containing iPP and oxo compound have lower decomposition temperature after UV irradiation. Finally, it can be said that the presence of iPP in HDPE matrix containing oxo compound can improve HDPE oxo‐biodegradablity. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45843.     

Preparation of poly(styrene‐b‐2‐hydroxyethyl acrylate) block copolymer using reverse iodine transfer polymerization

Reverse iodine transfer polymerizations (RITP) of 2‐h‐ydroxyethyl acrylate (HEA) were performed in N,N‐dimethylformamide at 75°C using AIBN as initiator. Poly(2‐hydroxyethyl acrylate) (PHEA) with M_n = 3300 g mol^?1 and M_w/M_n <1.5 were obtained. Homopolymerization of styrene in RITP was also carried out under similar conditions using toluene as solvent. The resulting iodo‐polystyrene (PS‐I) with (M_{n, SEC} = 607 g mol^?1, polydispersity index (PDI) = 1.31) was used as a macroinitiator for the synthesis of amphiphilic block copolymers based on HEA with controlled well‐defined structure. Poly(styrene‐b‐2‐hydroxyethyl acrylate) (PS‐b‐PHEA) with M_n = 13,000 g mol^?1 and polydispersity index (M_w/M_n) = 1.4 was obtained, copolymer composition was characterized using ¹H‐NMR and FTIR, whereas SEC and gradient HPLC were used to confirm the formation of block copolymer and the living character of polymer chains. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Kinetic study on biphasic recognition chiral extraction for separation of α‐cyclohexyl‐mandelic acid enantiomers

BACKGROUND: Chiral solvent extraction is a potentially attractive chiral separation technique. It is essential to know the intrinsic complexation kinetics for selection, design and operation of reactive extraction equipment and for reliable scale‐up. The objective of this research is to study the kinetics of biphasic recognition chiral extraction of α‐cyclohexyl‐mandelic acid (α‐CHMA) enantiomers using a modified Lewis cell. RESULTS: The experimental results demonstrate that the extraction reaction kinetics is fast, and the reactions are first order with respect to α‐CHMA and second order with respect to D‐IBTA, with forward rate constants of 6.54 × 10^?4 mol^?2 m⁶ s^?1 for S‐α‐CHMA and 6.84 × 10^?4 mol^?2 m⁶ s^?1 for R‐α‐CHMA. With increase of HP‐β‐CD concentration in aqueous phase, enantioselectivity increases, while the overall mass transfer coefficients decrease. CONCLUSIONS: Sufficient enantioselectivity and fast kinetics of extraction can be obtained in the BRCE system at HP‐β‐CD concentration of 0.1 mol L^?1 and D‐IBTA concentration of 0.2 mol L^?1. These data will be useful in the design of extraction processes. Copyright © 2012 Society of Chemical Industry     

Polyamide4‐block‐poly(vinyl acetate) via a polyamide4 azo macromolecular initiator: Thermal and mechanical behavior,biodegradation, and morphology

A series of polyamide4‐block‐poly(vinyl acetate)s were synthesized by the radical polymerization of vinyl acetate (VAc) using an azo macromolecular initiator composed of polyamide4 (PA4). The block copolymers were investigated by examining their molecular weight, structure, thermal and mechanical properties, biodegradation, and the morphology of the film surface. The compositions and molecular weights (Mw) ranging from 46,800 to 163,700 g mol^?1 of the block copolymers varied linearly with increasing molar ratio of VAc to azo‐PA4. The block copolymers have high melting points of 248.2–262.5°C owing to PA4 blocks and heats of fusion, which were linearly dependent on the PA4 content. The mechanical properties of the block copolymers were monotonically dependent on the composition, i.e., increasing the PA4 content increased the tensile strength, whereas increasing the poly(vinyl acetate) content increased the elongation at break. The morphology of the block copolymers suggested the appearance of microphase separation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42466.