Effect of pressure on phase behavior in polymer blends of poly(2,6-dimethyl-1,4-phenylene oxide) and poly(o-fluorostyrene-co-p-fluorostyrene) copolymers

The effect of pressure on miscibility and phase separation in blends of random copolymers of ortho- and para-fluorostyrene, P(o-FS-co-p-FS) and poly(2,6-dimethyl-1,4-phenylene oxide), PPO, has been studied by differential thermal analysis (DTA) at pressures up to 300 MPa. At 200 MPa the copolymers containing from 10 to 38 mol% p-FS are miscible with PPO below 230°C using the customary criterion of a single calorimetric glass transition temperature (T_g). Each blend undergoes phase separation upon annealing at higher temperatures at both atmospheric and elevated pressures indicating the presence of a lower critical solution temperature (LCST). When the phase behaviors of the 50/50 wt% blends are examined as a function of temperature and copolymer composition, a symmetric miscibility “window” can be observed in the resulting temperature-composition diagram with a maximum at about 22 mol% p-FS. In a complementary set of experiments, the pressure dependence of the phase boundary for the blend of PPO and P(o-FS-co-p-FS) in which the copolymer contained 29 mol% p-FS was studied. The temperature minimum of the phase boundary is at about 50 wt% PPO and is independent of pressure. The consolute temperature, T_c, increases at about 0.1₀°C/MPa up to 200 MPa and then becomes independent of pressure to reach an asymptotic value at around 270°C. Similar behavior is also observed for blends in which the copolymer composition contains either 16 or 23 mol% p-FS. In these blends the decrease of dT_c/dP at higher pressures may indicate that the negative volume of mixing approaches zero above 200 MPa. This study shows therefore, that pressure no longer plays a role in increasing the miscibility above 200 MPa.     

Miscibility and phase behavior in blends of poly(hydroxyether of bisphenol A) with poly(ethylene oxide-co-propylene oxide)

The miscibility of poly(hydroxyether of bisphenol A) (phenoxy) with a series of poly(ethylene oxide-co-propylene oxide) (EPO) has been studied. It was found that the critical copolymer composition for achieving miscibility with phenoxy around 60°C is about 22 mol % ethylene oxide (EO). Some blends undergo phase separation at elevated temperatures, but there is no maximum in the miscibility window. The mean-field approach has been used to describe this homopolymer/copolymer system. From the miscibility maps and the melting-point depression of the crystallizable component in the blends, the binary interaction energy densities, B_ij, have been calculated for all three pairs. The miscibility of phenoxy with EPO is considered to be caused mainly by the intermolecular hydrogen-bonding interactions between the hydroxyl groups of phenoxy and the ether oxygens of the EO units in the copolymers, while the intramolecular repulsion between EO and propylene oxide units in the copolymers contributes relatively little to the miscibility. © 1993 John Wiley & Sons, Inc.     

Thermally induced phase separation in homogeneous blends of poly(2,6-dimethyl-1,4-phenylene oxide) with poly(o-fluorostyrene-co-p-chlorostyrene) and with poly(o-fluorostyrene-co-o-chlorostyrene)

The phase separation behavior of initially compatible blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) with poly(o-fluorostyrene-co-p-chlorostyrene) [poly(oFS-co-pCIS)] and with poly(o-fluorostyrene-co-o-chlorostyrene) [poly(oFS-co-oCIS)] was studied by DSC. It was found that copolymers of poly(oFS-co-pCIS) containing between 15 and 62 mol % pCIS have shown no phase separation after annealing at temperatures up to 320°C. It was also observed that blends containing this copolymer with 74 mol % pCIS show phase separation at 250°C, which depended on blend composition. Additionally, all PPO/poly(oFS-co-oCIS) blends exhibit phase separation after annealing to a temperature of 230°C. Thermal degradation of the polymer blends was not observed at the temperatures studied.     

Miscibility behavior of blends of poly(alkyl methacrylate)s with poly(p-methylstyrene-co-methacrylonitrile)

The miscibility behavior of various poly(p-methylstyrene-co-methacrylonitrile) (pMSMAN)/poly(alkyl methacrylate)s blends was studied using differential scanning calorimetry. pMSMAN is miscible with poly(methyl methacrylate), poly(ethyl methacrylate), poly(n-propyl methacrylate), poly(isopropyl methacrylate), and poly(n-butyl methacrylate) over certain copolymer composition ranges, but is immiscible with poly(isobutyl methacrylate) and poly(n-amyl methacrylate). The width of the miscibility window decreases with increasing size of the pendant ester group of the poly(alkyl methacrylate), and is wider than that of the corresponding poly(p-methylstyrene-co-acrylonitrile) blend system. Various segmental interaction parameters are calculated using a binary interaction model. © 1995 John Wiley & Sons, Inc.     

Synthesis of block copolymers of poly(p-dioxanone) block poly(tetrahydrofuran)

Summary The triblock copolymers of poly(p-dioxanone)-b-poly(tetrahydrofuran)-b-poly(p-dioxanone) were synthesized by ring-opening polymerization of p-dioxanone in the presence of dihydroxyl poly(tetrahydrofuran)(PTHF) using stannous octoate (SnOct₂) as a catalyst. The effects of feed ratio, reaction time and reaction temperature on the copolymerization were investigated. It was found that the optimal reaction temperature and time were 80 °C and 42 hours, respectively, and the molar ratio of p-dioxanone/SnOct₂ (PDO/cat.) had little influence on the inherent viscosity of the copolymers. The triblock copolymers were characterized by various analytical techniques such as ¹H-NMR and DSC.     

Synthesis and characterization of anionic graft copolymers containing poly(ethylene oxide) grafts

Graft copolymers containing poly(ethylene oxide) side chain attached to maleic anhydride‐alt‐vinyl methyl ether (MA‐VME) copolymer were prepared by coupling MA‐VME and poly(ethylene glycol) monomethyl ether (MPEG) by esterification in DMF at 90°C. MPEG and dodecyl alcohol (DA) were grafted onto MA‐VME copolymer in o‐xylene at 140°C in the presence of p‐toluene sulfonic acid as catalyst. The molecular weights of MPEG were found to influence the rate of the grafting reaction and the final degree of conversion. The graft copolymers were characterized by IR, GPC, and ¹H‐NMR. DSC was used to examine thermal properties of the graft copolymers. The analysis indicates that grafts have phase‐separated morphology with the backbone and the MPEG grafts forming separate phases. The properties in aqueous solutions of these grafts were studied with respect to aggregation behavior and viscometric properties. In aqueous solution, the polymers exhibited polyelectrolyte behavior (i.e., a dramatic increase of the viscosity upon neutralization). Graft copolymers with DA have lower viscosities. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1138–1148, 2002     

Physicomechanical properties of poly(methyl methacrylate-co-N-arylmaleimides)

The article describes the effect of incorporating low mol fractions of N-o-tolymaleimide (MO)/N-p-tolymaleimide (MP) in poly(methyl methacrylate) (PMMA) on T_g, thermal behavior, mechanical, and optical properties. The glass transition temperature (T_g) of PMMA increased by 10–12°C upon incorporation of an ～ 0.026 mol fraction of N-arylmaleimides. A further increase of N-arylmaleimide content up to 0.1 mol fraction in the copolymers resulted in a further ～ 10°C increase in T_g. The tensile strength and % elongation decreased, whereas modulus increased with increasing maieimide content. The solar transmittance and % transmittance at higher wavelengths of the copolymer sheets having a low mol fraction of N-arylmalemides (i.e., 0.026–0.05) were comparable to PMMA. © 1995 John Wiley & Sons, Inc.     

Preparation and characterization of poly(ethylene-graft-ethylene oxide)

Graft copolymers containing poly(ethylene oxide) side chains attached to a polyethylene backbone were prepared by coupling of poly(ethylene-co-acrylic acid) (PEAA) and poly(ethylene oxide) monomethyl ethers (MPEO) by esterification in o-xylene at 140°C. The MPEO side chains had molecular weights of 750 to 5000. The chemical composition of the graft copolymers was analyzed by NMR and FT–IR spectroscopy. The weight fraction of the MPEO grafts in the graft copolymers was found to be around 0.4. The graft copolymers exhibited a phase-separated morphology with the backbones and the MPEO phase had a melting temperature 8–25°C lower than the corresponding MPEO homopolymers, as determined by DSC. The melting point of the crystalline phase formed by the PEAA main chains was close to that of the pure PEAA. Crystallinity was also confirmed by x-ray diffraction. © 1996 John Wiley & Sons, Inc.     

Miscibility and crystallization behavior of the solution‐blended sulfonated poly(phenylene oxide)/ poly(styrene‐co‐4‐vinyl pyridine) blend

The miscibility and crystallization behavior of the solution‐blended lightly sulfonated poly(phenylene oxide) (SPPO)/poly(styrene‐co‐4‐vinylpyridine) (PSVP) blend were investigated by conventional and modulated differential scanning calorimetry (MDSC). It was found that the original blend film is actually composed of a crystalline SPPO phase and a noncrystalline compatible SPPO–PSVP phase. The original phase‐segregated structure will evolve to a noncrystalline homogenous structure by subsequent high temperature annealing. The resulting good miscibility was attributed to two aspects: one is that the SPPO crystalline structure could be destroyed as annealing temperature is high enough; the other is that the acid–base interaction between the sulfonic group of SPPO and the pyridine ring of PSVP could promote mixing of different components effectively. And such acid–base interaction was demonstrated by ¹C NMR spectra. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2843–2848, 2001     

Miscibility of poly(methoxymethyl methacrylate) and poly(methylthiomethyl methacrylate) with poly(styrene-co-acrylonitrile) and poly(p-methylstyrene-co-acrylonitrile)

The miscibility of poly(methoxymethyl methacrylate) (PMOMA) and poly(methylthiomethyl methacrylate) (PMTMA) with poly(styrene-co-acrylonitrile) (SAN) and poly(p-methylstyrene-co-acrylonitrile) (pMSAN) was studied by differential scanning calorimetry. PMOMA is miscible with SAN having an acrylonitrile (AN) content around 30 wt %. However, PMOMA is immiscible with any of the pMSAN having AN contents between 9 and 36 wt % and with pMSAN having AN contents between 19 and 34 wt %. The miscibility of the blends enables the evaluation of various segmental interaction parameters.     

Reactively formed ENPT copolymers as compatibilizers in ternary blends of poly(ethylene naphthalate)/poly(pentamethylene terephthalate)/poly(ether imide)

The compatibility of ternary blends of poly(ethylene naphthalate)/poly(pentamethylene terephthalate)/poly(ether imide) (PEN/PPT/PEI) was studied by examining the transesterification of PEN and PPT. ENPT copolymers were formed in situ as compatibilizers between PPT and PEI components in ternary blends. Differential scanning calorimetric (DSC) results for ternary blends showed the immiscibility of PEN/PPT/PEI, but ternary blends of all compositions were phase‐homogeneous after heat treatment at 300°C for more than 60 min. Annealing samples at 300°C yielded amorphous blends with a clear, single glass transition temperature (T_g), as the final state. Additionally, ENPT copolymer improved the compatibility of ENPT/PPT/PEI blends, yielding a homogeneous phase in the ENPT‐rich compositions. The morphology of the ENPT/PPT/PEI blends was altered from heterogeneous to homogeneous by controlling the concentration of PPT in the ENPT copolymers as well as the concentration of the ENPT copolymers. Moreover, a homogeneous phase with a clear T_g was observed when the concentration of PPT in the ENPT copolymer fell to 70 wt% in the ENPT/PEI = 50/50 blends. Experimental results indicate how the concentration of PPT in the ENPT copolymer affects miscibility in the ENPT/PEI blends. POLYM. ENG. SCI. 46:337–343, 2006. © 2006 Society of Plastics Engineers     

Thermal analyses of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

Thermal analyses of poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(HB–HV)], and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(HB–HHx)] were made with thermogravimetry and differential scanning calorimetry (DSC). In the thermal degradation of PHB, the onset of weight loss occurred at the temperature (°C) given by T_o = 0.75B + 311, where B represents the heating rate (°C/min). The temperature at which the weight-loss rate was at a maximum was T_p = 0.91B + 320, and the temperature at which degradation was completed was T_f = 1.00B + 325. In the thermal degradation of P(HB–HV) (70:30), T_o = 0.96B + 308, T_p = 0.99B + 320, and T_f = 1.09B + 325. In the thermal degradation of P(HB–HHx) (85:15), T_o = 1.11B + 305, T_p = 1.10B + 319, and T_f = 1.16B + 325. The derivative thermogravimetry curves of PHB, P(HB–HV), and P(HB–HHx) confirmed only one weight-loss step change. The incorporation of 30 mol % 3-hydroxyvalerate (HV) and 15 mol % 3-hydroxyhexanoate (HHx) components into the polyester increased the various thermal temperatures T_o, T_p, and T_f relative to those of PHB by 3–12°C (measured at B = 40°C/min). DSC measurements showed that the incorporation of HV and HHx decreased the melting temperature relative to that of PHB by 70°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 90–98, 2001     

Miscibility and phase behavior in blends containing random copolymers of poly(ether ether ketone) and phenolphthalein poly(ether ether ketone)

The miscibility and phase behavior of polysulfone (PSF) and poly(hydroxyether of bisphenol A) (phenoxy) with a series of copoly (ether ether ketone) (COPEEK), a random copolymer of poly(ether ether ketone) (PEEK), and phenolphthalein poly(ether ether ketone) (PEK-C) was studied using differential scanning calorimetry. A COPEEK copolymer containing 6 mol % ether ether ketone (EEK) repeat units is miscible with PSF, whereas copolymers containing 12mol % EEK and more are not. COPEEK copolymers containing 6 and 12 mol % EEK are completely miscible with phenoxy, but those containing 24 mol % EEK is partially miscible with phenoxy. Moreover, a copolymer containing 17 mol % EEK is partially miscible with phenoxy; the blends show two transitions in the midcomposition region and single transitions at either extreme. Two T_gs were observed for the 50/50 blend of phenoxy with the coplymer containing 17 mol % EEK, whereas a single composition-dependent T_g appeared for all the other compositions. An FTIR study revealed that there exist hydrogen-bonding interactions between phenoxy and the copolymers. The strengths of the hydrogen-bonding interactions in the blends of the COPEEK copolymers containing 6 and 12 mol % EEK are the same as that in the phenoxy/PEK-C blend. However, for the blends of copolymers containing 17, 24, and 28 mol % EEK, the hydrogen-bonding interactions become increasingly unfavorable and the self-association of the hydroxyl groups of phenoxy is preferable as the content of EEK units in the copolymer increases. The observed miscibility was interpreted qualitatively in terms of the mean-field approach. © 1996 John Wiley & Sons, Inc.     

Compatibility of poly(2,6-dimethyl-1,4-phenylene oxide)/poly(fluorostyrene-co-chlorostyrene) blends

The compatibility of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) with random copolymers of ortho- and para-fluorostyrene as well as with ortho- and para-chlorostyrene of various copolymer compositions was examined. The compatibility was studied by DSC and visual observation of film clarity. It was found that copolymers of ortho-fluorostyrene with para-chlorostyrene containing 15–74 mol % p-CIS are compatible with PPO in all proportions. Compatibility of the PPO/poly-(ortho-fluorostyrene-co-ortho-chlorostyrene) system was observed for copolymers containing between 15 and 36 mol % ortho-chlorostyrene. Copolymers of para-fluorostyrene with para-chlorostyrene, as well as copolymers of para-fluorostyrene with ortho-chlorostyrene appear to be incompatible with PPO at 210°C.     

Gas transport and structural features of sulfonated poly(phenylene oxide)

The effect of ionomer structure on gas transport properties of membranes was investigated. For this purpose physical and transport properties of poly(phenylene oxide) (PPO) and its sulfonated derivative (SPPO) were compared. SPPO has a more rigid structure and a lower free volume, which determines low gas permeability and high permselectivity. Gas transport properties of two types of SPPO—PPO composite membranes with top layers prepared from solutions in methanol or N,N-dimethylacet-amide (DMA) were investigated. The use of SPPO solution in DMA leads to the formation of membranes with higher gas permeability. It was shown that DMA is a morphologically active solvent for SPPO. Strong complexes of SPPO with DMA are formed in solution and retained upon transition into the condensed state. The plasticizing effect of DMA on SPPO determines the high gas permeability of the membranes and is in agreement with their mechanical properties. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1439–1443, 1997     

Nitroxide‐terminated poly(styrene‐co‐diethyl fumarates) and derived block copolymers

Copolymerization of styrene (S) and diethyl fumarate (DEF) at 125°C in the presence of 2,2,6,6‐ tetramethylpiperidin‐1‐yloxyl radical (TEMPO) and initiated with a thermal initiator, 2,2′‐azobisisobutyronitrile (AIBN), was studied. The molar fraction of DEF in the feed, F_DEF, varied within 0.1–0.9. An azeotropic composition, (F_DEF)_A = 0.38, was found for the copolymerization under study. At F_DEF = 0.1–0.4, a quasi‐living process was observed, transforming to a retarded conventional radical copolymerization at a higher content of DEF in the initial mixtures. The obtained TEMPO‐terminated S‐DEF copolymers were used to initiate polymerization of styrene. Poly(styrene‐ co‐diethyl fumarate)‐block‐polystyrene copolymers were prepared with molecular weight distributions depending on the amount of inactive polymer chains in macroinitiators, as indicated by size‐exclusion chromatography. A limited miscibility of the blocks in the synthesized block copolymers was revealed by using differential scanning calorimetry. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2432–2439, 2002     

Studies on the sulfonation of poly(phenylene oxide) (PPO) and permeation behavior of gases and water vapor through sulfonated PPO membranes. III. Sorption behavior of water vapor in PPO and sulfonated PPO membranes

Water vapor absorption and desorption by poly(phenylene oxide) (PPO) and sulfonated PPO (SPPO) membranes were studied at a constant temperature of 30°C and over a broad range of water activity (0.05 ≤ a < 0.8) by the weighing method. The experimental sorption isotherms of both PPO and SPPO possessed a general sigmoidal shape, which suggested that they belong to type II; thus, the data may be quantitatively analyzed according to the BET or GAB equation for multilayer sorption processes. The number of site-bound water molecules per monomeric unit was increased by a factor of 150 after sulfonation of PPO. The features of the reduced absorption and desorption curves of both PPO and SPPO suggested that the sorption processes were non-Fickian. The diffusion coefficient calculated from the slope of the initial linear part of the curves showed concentration dependence. The permeability of water vapor through SPPO was more pressure-dependent than was that through PPO. The Flory–Huggins interaction parameter derived from experimental data on SPPO had a smaller value compared with that of PPO and was a monotonic increasing function of water activity in the low-activity region and then leveled off at a > 0.6, showing a corresponding initial decrease of the polymer–water interaction, which then gradually reached a certain stable value. Water clustering for SPPO was much less than that for PPO, which is clear proof of its higher hydrophilicity. The results from this study showed that SPPO could be an excellent dehumidification membrane material. © 1994 John Wiley & Sons, Inc.     

ABA triblock copolymers from poly(p‐dioxanone) and poly(ethylene glycol)

Poly(p‐dioxanone)–poly(ethylene glycol)–poly(p‐dioxanone) ABA triblock copolymers (PEDO) were synthesized by ring‐opening polymerization from p‐dioxanone using poly(ethylene glycol) (PEG) with different molecular weights as macroinitiators in N₂ atmosphere. The copolymer was characterized by ¹H NMR spectroscope. The thermal behavior, crystallization, and thermal stability of these copolymers were investigated by differential scanning calorimetry and thermogravimetric measurements. The water absorption of these copolymers was also measured. The results indicated that the content and length of PEG chain have a greater effect on the properties of copolymers. This kind of biodegradable copolymer will find a potential application in biomedical materials. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1092–1097, 2006     

Comparative studies of electrochemically deposited poly(o-toluidine) and poly(m-toluidine) films

Under galvanostatic deposition conditions poly(o-toluidine) exhibits a higher rate of polymerization than poly(m-toluidine). This observation is supported by results obtained by different characterization techniques such as spectrophotometry, scanning electron microscopy and thermogravimetric analysis. The monomer concentration was found to be the predominant parameter in obtaining selectively a conducting salt phase in both cases. However, the morphology of these polymeric films does not reveal any particular relationship with monomer concentration; instead a mixed morphology, i.e. a combination of granules and fibres, is observed. Finally, the thermal stability of poly(m-toluidine) is lower than that of poly(o-toluidine) with a shift of 190°C in the final decomposition temperature.     

Biodegradability of poly(ethylene terephthalate) copolymers with poly(ethylene glycol)s and poly(tetramethylene glycol)

Poly(ethylene terephthalate) copolymers were prepared by melt polycondensation of dimethyl terephthalate and excess ethylene glycol with 10–40mol% (in feed) of poly(ethylene glycol) (E) and poly(tetramethylene glycol) (B), with molecular weight (MW) of E and B 200–7500 and 1000, respectively. The reduced specific viscosity of copolymers increased with increasing MW and content of polyglycol comonomer. The temperature of melting (T_m), cold crystallization and glass transition (T_g) decreased with the copolymerization. T_m depression of copolymers suggested that the E series copolymers are the block type at higher content of the comonomer. T_g was decreased below room temperature by the copolymerization, which affected the crystallinity and the density of copolymer films. Water absorption increased with increasing content of comonomer, and the increase was much higher for E1000 series films than B1000 series films. The biodegradability was estimated by weight loss of copolymer films in buffer solution with and without a lipase at 37°C. The weight loss was enhanced a little by the presence of a lipase, and increased abruptly at higher comonomer content, which was correlated to the water absorption and the concentration of ester linkages between PET and PEG segments. The weight loss of B series films was much lower than that of E series films. The abrupt increase of the weight loss by alkaline hydrolysis is almost consistent with that by biodegradation.