Microstructure elucidation of poly(epichlorohydrin) modified with thiol compounds using one- and two-dimensional NMR spectroscopy

Poly(epichlorohydrin) has been modified chemically using aromatic and aliphatic thiol compounds. The NMR results show that using both aromatic and aliphatic thiols, one achieves degrees of modification of up to 90% without any elimination side reaction. As a consequence no degradative chain-scission takes place. A microstructural analysis of the modified polymers has been carried out by ¹³C NMR, ¹H NMR and ¹³C DEPT spectroscopy. Additionally, 2D heteronuclear correlated spectroscopy (HMQC and HMBC) were used in order to determine the chemical shifts of quaternary carbons.     

Dielectric relaxation study of atactic poly(epichlorohydrin)/poly(3-hydroxybutyrate) blends

Binary blends of atactic poly(epichlorohydrin) (aPECH) and poly(3-hydroxybutyrate) (PHB) were investigated as a function of blend composition and crystallization conditions by dielectric relaxation spectroscopy. The quenched samples were found to be miscible in the whole composition range by detecting only one glass transition relaxation, for each composition, which could be closely described by the Gorden-Taylor equation. The cold-crystallized blends displayed two glass transition relaxations at all blend ratios indicating the coexisting of two amorphous populations: a pure aPECH phase dispersed mainly in the interfibrillar zones and a mixed amorphous phase held between crystal lamellae. The interlamellar trapping of aPECH was small and decreases with increasing the overall PHB content in the blend. At high crystallization temperatures the aPECH molecules was found to reside mainly in the interfibrillar regions due to its high mobility relative to the crystal growth rate of PHB. Our results suggest that because the intersegmental interaction in aPECH/PHB blends is weak, the mobility of the amorphous component at a given crystallization temperature decides diluent segregation.     

Modification of poly(epichlorohydrin) with nadimide derivatives and their curing reaction

Chemical modification of poly(epichlorohydrin) (PECH) with nadimide derivatives using 1,8-diazabicyclo (5.4.0)?7 undecene to catalyze the substitution of the chlorine atom by acid compounds (DBU method) was accomplished. The linear polyethers obtained showed a degree of substitution from 5–80%, depending on time and temperature reaction. The T_g of modified polymers and Ea, calculated in the cure reactions, increases with substitution degree. Residual enthalpies were observed in all cases, which suggests that the curing reaction is incomplete. TGA measurements showed that the degradation has a greater dependence on the modification degree than on the introduced pendant group. © 1994 John Wiley & Sons, Inc.     

Chemical modification of poly(vinyl chloride) by nucleophilic substitution

The reaction of poly(vinyl chloride) (PVC) in nucleophile (Nu)/ethylene glycol (EG) or Nu/N,N-dimethylformamide (DMF) solution was found to result in the substitution of Cl in PVC with Nu from solution, in addition to the straight elimination of HCl, both of which led to the dechlorination of PVC. Examined Nu⁻ were I⁻, SCN⁻, OH⁻, N₃⁻, and the phthalimide anion. For the Nu/EG solution, elimination was favoured over substitution for all Nu⁻. The ratio of substitution to dechlorination was notable, descending in the order OH⁻ > SCN⁻ = N₃⁻ > phthalimide anion > I⁻. For the Nu/DMF solution, the ratio of substitution to dechlorination was high, in the order SCN⁻ > N₃⁻ > I⁻ > phthalimide anion. In both cases, the orders of the ratios were similar to those of the nucleophilic reactivity constant, I⁻ > SCN⁻ > N₃⁻ > phthalimide anion, except for I⁻. The low ratio for I⁻ was attributable to the elimination of HI after the substitution of Cl in PVC with I in solution, because I⁻ is a strong nucleophile, as well as an excellent leaving group. Comparing the effect of EG and DMF on the substitution of Cl in PVC with Nu in solution, the ratio of substitution to dechlorination was higher for I⁻, SCN⁻, N₃⁻, and the phthalimide anion in DMF than in EG. The substitution of Cl in PVC with Nu in solution was found to occur preferentially in DMF versus EG.     

Assessment of amination reactions via nucleophilic aromatic substitution using conventional and eco-friendly energies

The efficiency of conventional heating energy source compared with Infrared (IR), Ultrasound (US), Microwave and the simultaneous combination US–IR eco-friendly approaches for preparation of new N-(5-R¹ _-amino-2-nitrophenyl)acetamides and 5-R¹-amino-2-nitroaniline by Nucleophilic Aromatic Substitution (S_NAr) via addition–elimination reactions on the halogens F, Cl, Br, I, employing amines as nucleophiles were explored. Moreover, phenyldiazenyl derivatives in good yields by an oxidative one-pot S_NAr-based amination reaction from an unusual oxidation of 2-phenylhydrazinyl derivatives in DMSO was prepared.     

Thermal and crystallization characteristics of poly(trimethylene terephthalate)/poly(ethylene naphthalate) blends

Poly(trimethylene terephthalate) (PTT)/poly(ethylene naphthalate) (PEN) blends were miscible in the amorphous state in all of the blend compositions studied, as evidenced by a single, composition-dependent glass transition temperature (T_g) observed for each blend composition. The variation in the T_g value with the blend composition was well predicted by the Gordon-Taylor equation, with the fitting parameter being 0.57. The cold-crystallization peak temperature decreased with increasing PTT content, while the melt-crystallization peak temperature decreased with increasing amount of the minor component. The subsequent melting behavior after both cold- and melt-crystallization exhibited melting point depression, in which the observed melting temperatures decreased with increasing amount of the minor component. During melt-crystallization, both components in the blends crystallized concurrently just to form their own crystals. The blend with 60% w/w of PTT exhibited the lowest total apparent degree of crystallinity.     

The miscibility of poly(vinyl alcohol)/poly(N-vinylpyrrolidone) blends investigated in dilute solutions and solids

Poly(vinyl alcohol) (PVA) (polymer A) and poly(N-vinylpyrrolidone) (PVP) (polymer B) are known to form a thermodynamically miscible pair. In the present study the conclusion on miscibility of PVA/PVP solid blends, confirmed qualitatively (DMTA, FTIR) and quantitatively (DSC, χ_AB = − 0.69 at 503 K) is compared with the miscibility investigations of PVA/PVP solution blends by the technique of dilute solution viscometry. The miscibility of the ternary (polymer A/ polymer B/ solvent) system is estimated on the basis of experimental and ideal values of the viscosity parameters k, b and [η]. It is found that the conclusions on miscibility or nonmiscibility drawn from viscosity measurements in dilute solution blends depend: (i) on the applied extrapolation method used for the determination of the viscosity interaction parameters, (ii) on the assumed definition of the ideal values and (iii) on the thermodynamic quality of the solvent, which in the case of PVA depends on its degree of hydrolysis. Hence, viscometric investigations of dilute PVA/PVP solution blends have revealed that viscometry, widely used in the literature for estimation of polymer-polymer miscibility can not be recommended as a sole method to presume the miscibility of a polymer pair.     

Compatibility and phase structure of binary blends of poly(lactic acid) and glycidyl methacrylate grafted poly(ethylene octane)

This work study is the compatibility, phase structure, and component interaction of poly(lactic acid) (PLA) and glycidyl methacrylate grafted poly(ethylene octane) (GMA-g-POE denoted as mPOE) blend by Fourier transform infrared (FTIR) spectra, dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and wide-angle X-ray diffraction (WAXD), respectively. All the binary blend compositions exhibit two distinct glass transition temperatures corresponding to the mPOE-rich and PLA-rich phases, respectively. Moreover, these two peaks approach each other with increasing mPOE content, indicating partial compatibility between the PLA and mPOE. Chemical reactions between the end carboxyl groups of the PLA and epoxy groups of the mPOE are considered as the driving force of the enhanced compatibility. They lead to an increase in viscosity of the blends and a decrease in the structural symmetry of PLA. This result brings about a decrease in the spherulite growth rate and the degree of crystallinity. Glass transition temperature (T_g) depression of mPOE is attributed to the negative pressure imposed on the dispersed rubber phase, resulting from differential contraction due to the thermal shrinkage mismatch upon cooling from the melt state. The negative pressure in the dispersed particles, in turn, would cause a dilational effect for the matrix ligament between the particles, and therefore increases the ductility and toughness of PLA.     

Synthesis and properties of polymer brushes composed of poly(diphenylacetylene) main chain and poly(ethylene glycol) side chains

Novel cylindrical polymer brushes consisting of poly(diphenylacetylene) main chain and poly(poly(ethylene glycol) methyl ether monomethacrylate) (PPEGMA) side chains were synthesized by the diphenylacetylene macromonomer or side chain initiated atom transfer radical polymerization (ATRP) of poly(ethylene glycol) methyl ether monomethacrylate (PEGMA) from an bromo isobutyryl-bearing poly(diphenylacetylene) (poly(BrDPA)) method. The diphenylacetylene macromonomer, namely, DPA-PPEGMA, were prepared by the ATRP of PEGMA from bromo isobutyryl-bearing diphenylacetylene. DPA-PPEGMA was polymerized successfully with WCl₆-Ph₄Sn catalyst to give high molecular weight polymer brushes poly(DPA-PPEGMA). Meanwhile, polymer brushes (PDPA-g-PPEGMA) were obtained by ATRP of PEGMA from poly(BrDPA). The molecular weight of the side chains of PPEGMA could be controlled simply by modulating the ATRP time. The macromonomer and polymer brushes are soluble in nonpolar solvents such as toluene and chloroform. The polymers of poly(BrDPA) and poly(DPA-PPEGMA) absorb in the longer wavelength region, with two peaks at around 370 and 414 nm. The polymers are thermally stable and exhibit double crystallization and melting peaks during the cooling and heating scans.     

Synthesis and applications of cross-linked poly(diallyldimethyl ammonium chloride) and its derivative copolymers as efficient phase transfer catalyst for nucleophilic substitution reactions

Cross-linked poly(diallyldimethylammonium chloride) and its derivative copolymers were synthesized and used as phase transfer catalyst in the nucleophilic substitution reaction especially halogen exchange reactions. In addition, the effect of hydrophilic-hydrophobic character of the polymers in the nucleophilic reactions was investigated.     

Poly(arylether amides) and poly(aryletherketone amides) via aromatic nucleophilic substitution reactions of self‐polymerizable AB and AB2 monomers

Two new extended self‐polymerizable AB monomers, N‐(4‐fluorobenzoyl)‐4‐amino‐4′‐hydroxydiphenylether and N‐(4‐fluorobenzoyl)‐4‐amino‐4′‐hydroxybiphenyl, were prepared. The monomers were homopolymerized and copolymerized to high‐molecular‐weight, linear poly(arylether amides) in N‐methylpyrrolidone (NMP)/toluene in the presence of potassium carbonate at elevated temperature. The polymers retained NMP up to 200 °C. Samples containing small amounts of the solvent (5–10 wt %) were soluble in polar aprotic solvents. However, after complete removal of the NMP, the polymers were only soluble in strong acids such as sulfuric acid and methanesulfonic acid (MSA). The polymers, which had intrinsic viscosities of 0.57–1.49 dL/g (30.1 ± 0.1 °C in MSA), were semicrystalline with melting temperatures above 400 °C. Two new self‐polymerizable AB₂ amide monomers, N,N′‐bis(4‐fluorobenzoyl)‐3,4‐diamino‐4′‐hydroxydiphenylether and N,N′‐bis(4‐fluorobenzoyl)‐3,5‐diamino‐4′‐hydroxybenzophenone, were also prepared and polymerized to give a hyperbranched poly(arylether amide) and a hyperbranched poly(aryletherketone) amide. The arylfluoride‐terminated, amorphous polymers had intrinsic viscosities of 0.34 and 0.24 dL/g (30.0 ± 0.1 °C in m‐cresol), glass‐transition temperatures of 210–269 °C, and were soluble in a wide variety of organic solvents. Matrix‐assisted laser desorption/ionization time‐of‐flight analysis indicated that the components of the low‐molecular‐weight fractions contained cyclic structures. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2374–2389, 2003     

Chemical Modification of Poly(epichlorohydrin) Using Montmorillonite Clay

Cationic ring opening polymerization of epichlorohydrin (1) and acetic anhydride in the presence of Maghnite- H (Mag-H＋) as a catalyst afforded, ω-diacetylated poly(epichlorohydrin) (P1) in a moderate yield and molecular weight without formation of side products and degradation. P1 was chemically modified with morpholine (2), piperidine (3) and pyrrolidine (4) into the corresponding new functional poly(epichlorohydrin)s (P2—P4) in a moderate reaction conversion . The conversion of P1 into P2—P4 was confirmed by using FTIR and NMR spectroscopy and the yield was calculated from the elemental analysis data according to the mole fraction concept. The obtained functional polymers were further characterized by thermal analysis which showed a substantial increase of the glass transition temperature (Tg). Thus, the chemical modification of α,ω-acetylated PECH using Mag-H＋ offers a simple method for obtaining functional polymers. Mag-H＋ is a montmorillonite sheet silicate clay exchanged with proton.     

Morphology control of sulfonated poly(ether ketone ketone) poly(ether imide) blends and their use in proton-exchange membranes

Polymer blends based on sulfonated poly(ether ketone ketone) (SPEKK) as the proton-conducting component and poly(ether imide) (PEI) as the second component were considered for proton-exchange membranes (PEMs). The PEI was added to improve the mechanical stability and lower the water swelling in the fuel cell environment. Membranes were cast from solution using N-methyl-2-pyrrolidone (NMP) and dimethylacetamide (DMAc). The ternary, polymer/polymer/solvent, phase diagram was determined to provide guidance on how to control the morphology during solvent casting of blend membranes.

For blends of SPEKK (ion-exchange capacity = 2 mequiv/g) with PEI as the minority component, the morphology consisted of dispersed particles of 0.5–6 μm. Larger particles were achieved by increasing the PEI content and/or lowering the casting temperature. High-temperature annealing after solution casting did not affect the morphology of blend membranes, due to the low mobility and compatibility of the two polymers.

The possible use of SPEKK/PEI blends in PEMs is discussed in terms of existing theories of ion transport in polymers.     

Molecular dynamics of poly(ATRIF) homopolymer and poly(AN-co-ATRIF) copolymer investigated by dielectric relaxation spectroscopy

Aiming to develop new dielectric polymers containing CN and F groups with strong dipole moments, a novel copolymer of acrylonitrile (AN) and 2,2,2-trifluoroethyl acrylate (ATRIF) was synthesized in acetonitrile by free radical process as well as the respective homopolymer (poly(ATRIF)). The copolymer’s composition and microstructure were analyzed by FTIR, ¹H and ¹³C NMR spectroscopy and SEC. The molar incorporation of AN determined in the copolymer by NMR was 58 mol%. Thermogravimetric analysis of poly(AN-co-ATRIF) copolymer showed good thermal stability comparatively to the fluorinated homopolymer.Both copolymer, poly(AN-co-ATRIF), and homopolymer, poly(ATRIF), were dielectrically characterized over a frequency range from 10⁻¹ to 10⁶ Hz, and in a temperature range from 223 to 393 K. The dominating relaxation process detected in both materials is the α-relaxation, associated with the dynamic glass transition. A VFTH temperature dependence of the relaxation times (τ) was found for both materials, as characteristic of cooperative processes, from which the respective glass transition temperatures (T_g(τ = 100 s)) were estimated, which differ ∼40 K, the one of the copolymer being higher (307 K) in accordance to the calorimetric analysis. This effect was attributed to a higher stiffness of the backbone in the copolymer originated by the inclusion of the acrylonitrile groups. Both relaxation functions have the same breath of relaxation times allowing constructing a single master curve, indicating similar non-exponential character. A less fragile behavior was found for the copolymer. This was rationalized in a more straightforward way by the free volume approach instead from a correlation between fragility and intermolecular coupling. It was found that in the copolymer the free volume increases at a lower rate with the temperature increase. It was inferred from the VFTH temperature dependence of the dc conductivity and low values of the decoupling index that ion motion is significantly influenced by the dynamics of the α-process.     

Synthesis and characterization of biodegradable aliphatic copolyesters with poly(ethylene oxide) soft segments

A series of multiblock poly(ether-ester)s based on poly(butylene succinate) (PBS) as the hard segments and hydrophilic poly(ethylene oxide) (PEO) as the soft segments was synthesized with the aim of developing degradable polymers which could combine the mechanical properties of high performance elastomers with those of flexible plastics. The aliphatic poly(ether-ester)s were synthesized by the catalyzed two-step transesterification reaction of dimethyl succinate, 1,4-butanediol and α,ω-hydroxyl terminated poly(ethylene oxide) (PEO, = 1000 g/mol) in bulk. The content of soft PEO segments in the polymer chains was varied from about 10 to 50 mass%. The effect of the introduction of the soft PEO segments on the structure, thermal and physical properties, as well as on the biodegradation properties was investigated. The composition and structure of these aliphatic segmented copolyesters were determined by ¹H NMR spectroscopy. The molecular weights of the polyesters were verified by gel permeation chromatography (GPC), as well as by viscometry of dilute solutions and polymer melts. The thermal properties were investigated using differential scanning calorimetry (DSC). The degree of crystallinity was determined by means of DSC and wide-angle X-ray scattering. A depression of melting temperature and a reduction of crystallinity of the hard segments with increasing content of PEO segments were observed. Biodegradation of the synthesized copolyesters, estimated in enzymatic degradation tests in phosphate buffer solution with Candida rugosa lipase at 37 °C was compared with hydrolytic degradation in the buffer solution. The weight losses of the samples were in the range from 2 to 10 mass%. GPC analysis confirmed that there were significant changes in molecular weight of copolyesters with higher content of PEO segments, up to 40% of initial values. This leads to conclusion that degradation mechanism of the poly(ether-ester)s based on PEO segments occurs through bulk degradation in addition to surface erosion.     

Chemical modification of poly(lactic acid) and its use as matrix in poly(lactic acid) poly(butylene adipate-co-terephthalate) blends

Poly(lactic acid), PLA, was chemically modified with maleic anhydride (MA) by reactive extrusion. The effect of this modification on molar mass (MM) and acidity was assessed by means of size-exclusion chromatography (SEC) and titration, respectively. PLA MM decreased in the presence of MA solely and of MA and peroxide. Reduction in MM was monitored by the increase in acidity. PLA blends containing poly(butylene adipate-co-terephthalate) (PBAT) were prepared through different mixing protocols, PLA/PBAT, PLA-g-MA/PBAT and PLA/PBAT/MA/peroxide (PLA/PBAT in situ). SEC results and rheological properties revealed reduction in MM and viscosity of the modified blends. PLA/PBAT presented increase in MM and bimodal MM distribution. The calculated interfacial tension was significantly lower for the modified blends, despite the lower average particle area of PLA/PBAT. Surprisingly, the modified blends presented higher yield strength than that predicted by the rule of mixtures, which might indicate interfacial reactions.     

Pervaporation of alcohol-toluene mixtures through polymer blend membranes of poly(acrylic acid) and poly(vinyl alcohol)

Homogeneous membranes were prepared by blending poly(acrylic acid) with poly(vinyl alcohol). These blend membranes were evaluated for the selective separation of alcohols from toluene by pervaporation. The flux and selectivity of the membranes were determined both as a function of the blend composition and of the feed mixture composition. The results showed that a polymer blending method could be very useful to develop new membranes with improved permselectivity. The pervaporation properties could be optimized by adjusting the blend composition. All the blend membranes tested showed a decrease in flux with increasing poly(vinyl alcohol) content for both methanol—toluene and ethanol—toluene liquid mixtures. The alcohols permeated preferentially through all tested blend membranes, and the selectivity values increased with increasing poly(vinyl alcohol) content. The pervaporation characteristics of the blend membranes were also strongly influenced by the feed mixture composition. The fluxes increased exponentially with increasing alcohol concentration in the feed mixtures, whereas the selectivities decreased for both liquid mixtures.     

Stereoselective nucleophilic substitution of poly(vinyl chloride) with potassium 4‐acetamidothiophenolate

The nucleophilic substitution reaction of poly(vinyl chloride) (PVC) with potassium 4‐acetamidothiophenolate was performed in a cyclohexanone solution. The quantitative microstructural analysis, as a function of the conversion, was followed by ¹³C NMR spectroscopy. Through a comparison of the microstructural changes with the degree of substitution, a small fraction of mmr tetrads was found to react occasionally with the central chlorine of the mr triad instead of the mm, such as for sodium benzenethiolate (NaBT). This conclusion was confirmed by Fourier transform infrared results. However, unlike NaBT, the evolution of the glass‐transition temperature (T_g) with the degree of conversion changed with the degree of substitution similarly to the ratio of the extents to which mmr and rrmr structures intervened in the substitution reaction. From these studies, it followed that the specific interactions due to the polar nature of the nucleophile enhanced the molecular‐microstructure‐based mechanisms, which were responsible for T_g. Such a novel quantitative correlation, compared with more tentative ones obtained previously, presents valuable insight into the role of the stereochemical microstructure in the glass‐transition process in PVC. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1857–1867, 2004     

A new class of aromatic poly(ether-ketone benzoxazole) copolymers by nucleophilic polycondensation: Synthesis and properties

A number of difluorophenyl benzoxazole (DB) monomers and 4,4′-difluorobenzophenone (DFB) were subjected to fluoro-displacement with two different phenoxides in a polar aprotic solvent. A series of novel poly(ether-ketone benzoxazole) copolymers (PAEKBOs) were more readily prepared, in which the generation of aryl-ether linkages was the copolymer forming reaction. The effects of monomer structure and polymerization conditions on the polymerization results and polymer solubility were analyzed. Copolymers 1, 2-X, 4 and 6 were obtained with high molecular weight. Copolymers 2-X and 4 showed organic solubility, especially the copolymers 2-X could dissolve in many usual organic solvents at the solid concentration of up to 20 wt%. TGA and DSC measurements confirmed that the copolymers 2-X, 4 and 6 were thermally stable up to 500 °C, and showed single enhanced T_gs and an amorphous morphology. The copolymers behaved in many respects as engineering thermoplastics. The properties and the processability of several members of the PAEKBOs offer the prospect of being candidates to substitute poly(ether-ether-ketone) (PEEK) using in a wider usage temperature range and being high performance materials for many applications as films, coatings for optical and electronic devices and gas separation membranes.     

Effect of small amount of poly(ethylene naphthalate) on isothermal crystallization and spherulitic morphology of poly(trimethylene terephthalate)

The effect of a small amount of poly(ethylene naphthalate) (PEN) in its blends with poly(trimethylene terephthalate) (PTT) on isothermal melt-crystallization kinetics and spherulitic morphology of the blends was thoroughly investigated. The maximum PEN content in the blends was 9 wt%. Due to the single composition-dependent glass transition temperature (T_g) that was observed for each blend, these blends appeared to be miscible in the amorphous state. After isothermal crystallization from the melt state, the neat PTT and its blends with PEN exhibited either double or triple melting endotherms. The triple endothermic peaks were observed in both the neat PTT and the blends when being crystallized at crystallization temperatures (T_c) of less than or equal to 195 °C. The equilibrium melting temperature () for the neat PTT was determined based on the linear Hoffman–Weeks extrapolative method to be 248 °C. Such values for the blends were found to decrease with the addition and increasing amount of PEN. Both the neat PTT and the blends were isothermally crystallized over the T_c range of 190–205 °C. At a given T_c, the 97PTT/3PEN blend exhibited a half-time of crystallization (t_0.5) value that was lower, while it exhibited reciprocal half-time (), Avrami rate constant (K_A), and spherulitic growth rate (G) values that were greater, than those of the neat PTT. With further increase in the PEN content, the t_0.5 value increased, while the , K_A, and G values decreased. Analysis of the G values based on the Lauritzen–Hoffman's (LH) secondary nucleation theory showed that the neat PTT and the 91PTT/9PEN blend exhibited a regime II→III transition at 194 °C (467.2 K), while no regime transition was observed for the other two blends. The lateral and the fold surface free energies (σ and σ_e) and the work of chain folding (q) for the neat PTT and the blends were 19.4, 30.2–46.3 erg cm⁻², and 2.4–3.6 kcal mol⁻¹, respectively. Lastly, the effect of both the T_c and the PEN content on morphology and texture of the PTT spherulites was also investigated and the results showed that the texture of the spherulites became coarser with increasing T_c and PEN content.