Poly(methyl acrylate)/poly(hydroxyethyl acrylate) sequential interpenetrating polymer networks. Miscibility and water sorption behavior

Sequential poly(methyl acrylate)/poly(hydroxyethyl acrylate) interpenetrating polymer networks with different poly(hydroxyethyl acrylate) contents were prepared by free radical polymerization of hydroxyethyl acrylate inside the previously polymerized poly(methyl acrylate) network. Differential scanning calorimetry on dry samples shows that the interpenetrating polymer networks exhibit phase separation, and no differences are found between the glass transition temperatures of the two phases present in the interpenetrating polymer network and those of the pure components. Thermally stimulated depolarization current experiments were used to study the influence of water sorption on the mobility of the different molecular groups in the poly(hydroxyethyl acrylate) phase of the interpenetrating polymer network. Isothermal water sorption of the interpenetrating polymer networks and pure poly(methyl acrylate) and poly(hydroxyethyl acrylate) networks is analyzed with different theories to compare the behavior of the poly(hydroxyethyl acrylate) phase in the interpenetrating polymer networks with that of the pure poly(hydroxyethyl acrylate) network. Diffusion coefficients of water in the interpenetrating polymer networks are obtained by means of dynamic sorption experiments. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1587–1599, 1999     

Poly(N-phenyl-2-hydroxytrimethylene amine): Its blends with poly(ϵ-caprolactone) and water-soluble polyethers

A new polymer with pendant hydroxyl groups, namely, poly(N-phenyl-2-hydroxytrime-thylene amine) (PHA), was synthesized by a direct condensation polymerization of aniline and epichlorohydrin in an alkaline medium. The new polymer is amorphous with a glass transition temperature (T_g) of 70°C. Blends of PHA with poly(ϵ-caprolactone) (PCL), as well as with two water-soluble polyethers, poly(ethylene oxide) (PEO) and poly(vinyl methyl ether) (PVME), were prepared by casting from a common solvent. It was found that all the three blends were miscible and showed a single, composition dependent glass transition temperature (T_g). FTIR studies revealed that PHA can form hydrogen bonds with PCL, PEO, and PVME, which are driving forces for the miscibility of the blends. © 1997 John Wiley & Sons, Inc.     

Fibers from a low dielectric constant fluorinated polyimide: Solution spinning and morphology control

Control of the internal morphology of wet-spun fibers from a fluorinated polyimide has been achieved by varying the rate of polymer coagulation through adjustments in nonsolvent/solvent miscibility and precipitation strength of the coagulation bath. Filament internal morphologies ranged from very porous or sponge-like to fully solid. Intermediate structures included fibers containing a spongy core with a nonporous skin, sponge-like fibers containing large voids, and a relatively solid material containing randomly spaced small voids. The cross-sectional shape of the fiber is dependent upon the coagulation process as well as the volume contraction of the initial extrudate. Drawn fibers (3×) retained the original asspun cross-sectional shape and also lost porosity. Mechanical properties of poly(6FDA-4BDAF) fibers have an inverse relationship to filament porosity. Maximum modulus and break strength for drawn fibers is approximately 6 CPa and 200 MPa, respectively. Asspun mechanical properties were dependent upon the processing conditions and have moduli between 0.4–3.0 Gpa and break strengths of 10–160 MPa. A dielectric constant of 2.50 for nonporous films was measured over a frequency range between 1.0 MHz to 1.8 GHz, showing little dispersion. © 1997 John Wiley & Sons, Inc.     

Poly(4-methylpentene-1)/hydrogenated oligo (cyclopentadiene) blends: Miscibility,tensile stress–strain,and dynamic mechanical behaviors

This article discusses the influence of the oligomeric resin, hydrogenated oligo(cyclopentadiene) (HOCP), on the morphology, and thermal and tensile mechanical properties of its blends with isotactic poly(4-methylpentene-1) (P4MP1). The P4MP1 and HOCP are found not miscible in the melt state. P4MP1/HOCP blends after solidification contain three phases: the crystalline phase of P4MP1, an amorphous phase of P4MP1, and an amorphous phase of HOCP. From optical micrographs obtained at 150°C, it is found that the solidified blends show a morphology constituted by P4MP1 microspherulites and small HOCP domains homogeneously distributed in intraspherulitic regions. DSC and DMTA results show that the blends present two glass transition temperatures (T_g) equal to the T_gs of the pure components. The tensile mechanical properties have been investigated at 20, 60, and 120°C. At 20°C both the HOCP oligomer and the amorphous P4MP1 are glassy, and it is found that all the blends are brittle and the stress–strain curves have equal trends. At 60°C the HOCP oligomer is glassy, whereas the amorphous P4MP1 is rubbery. The tensile mechanical properties at 60°C are found to depend on blend composition. It is found that the Young's modulus, the stresses at yielding and break points slightly decrease with HOCP content in the blends and these results are related to the decrease of blend crystallinity. The decrease of the elongation at break is accounted for by the presence of glassy HOCP domains that act as defects in the P4MP1 matrix, hampering the drawing. At 120°C both the amorphous phases are rubbery. It is found decreases of Young's modulus, stresses at yielding and break points. These results have been related to the decrease of blend crystallinity and to the increase of the total rubbery amorphous phase. Moreover, it is found that the blends present elongations at break equal to that of pure P4MP1. This constancy is attributed to: (a) at 120°C the HOCP domains are rubbery and their presence seems not to disturb the drawing of the samples; (b) a sufficient number of the tie-molecules and entanglements of P4MP1 present in the blends. In fact, although the numbers of tie-molecules and entanglements decrease in the blends, increasing the HOCP oligomer, they seem to be enough to keep the material interlaced and avoid earlier rupture. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1269–1277, 1997     

Poly(vinyl pyrrolidone-co-vinyl acetate)–cellulose acetate blends as novel pervaporation membranes for ethanol–ethyl tertio-butyl ether separation

The design of high-performance pervaporation membranes for the selective removal of ethanol from ethyl t-butyl ether (ETBE) was performed by using the polymer blending method. Binary blends of cellulose acetate or cellulose triacetate with a specific copolymer, poly(vinyl pyrrolidone-co-vinyl acetate), were studied by pycnometry, differential scanning calorimetry, infrared spectroscopy, solvent–mixture sorption and pervaporation.The sorption extent and especially the permeability of the blend membranes to the ethanol–ETBE azeotropic mixture increases greatly with the copolymer content with quasi-constant and high selectivity. This behavior is attributed to the specific interactions of amide C=O groups (a strong Lewis-base) in the copolymer with ethanol. The resulting high-performance membranes were stable at low temperatures but showed some performance alteration, at temperatures exceeding 80°C, because of copolymer extraction by the solvent mixture. The different behaviors of the same membrane at high and low temperatures were explained in terms of copolymer chain reptation, which was possible in the rubbery state but not in the glassy state. A crosslinking of the two polymers via urethane bonds led to perfectly stable high-performance membranes for the target application. © 1997 John Wiley & Sons, Ltd.     

Strength of hydrogen bonding in the novolak-type phenolic resin blends

The specific interaction strength of novolak-type phenolic resin blended with three similar polymers [i.e., poly(ethylene oxide) (PEO), poly(ethylene glycol) (PEG), and poly(vinyl alcohol) (PVA)] were characterized by means of glass transition temperature behavior and Fourier transform infrared (FTIR) spectroscopy. The interassociation formed within phenolic blends with the addition of a modifier not only overcomes the effect of self-association of the phenolic upon blending, but also increases the strength of phenolic blend. The strength of interassociation within the phenolic blend is the function of the hydrogen bonding group of a modifier, in increasing order, is phenolic/PVA, phenolic/PEG, and phenolic/PEO blend, corresponding to the result of “q” value in the Kwei equation. The FTIR result is in agreement with the inference of T_g behavior. In addition, the fact that the specific strength of hydrogen bonding of hydroxyl–hydroxyl is stronger than that of hydroxyl–ether can also be concluded. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1721–1729, 1998     

Spectroscopic characterization of micro-phase separated blends of polystyrene/polymethyl methacrylate (PS/PMMA)

An investigation of the miscibility behaviour in polystyrene/ polymethyl methacrylate (PS/PMMA) blends of various compositions under different evaporations protocols using Fourier transform infrared (FT-IR) and Raman Spectroscopic techniques took place in the study. Solvent selection and evaporation rates, coupled with variations in the blend composition resulted in completely different miscibility behaviour for these systems. In particular, it was found that blends with low PMMA content result in systems that exhibit PMMA domains of less than 7 microns on average. Finally, depth profiling studies of the PMMA moiety in the PS matrix show that the distribution of the low content phase is highly affected by the solvent selection as well as the blend composition.     

P(HB-co-HV)/PVPh的相容性与聚集态结构

采用差热扫描分析、红外光谱、固体核磁、小角X光散射等方法研究了聚(β-羟基丁酸酯-co-β-羟基戊酸酯(P(HB-co-HV))/聚(对-羟基苯乙烯)(简称PVPh)共混物的相容性和形态。结果表明两组分间形成较强的分子间氢键,形成完全相容的共混体系。固体核磁结果表明P(HB-co-HV)/PVPh(50/50)在3.4nm尺寸上是完全均相的。小角X光散射结果表明,在等温结晶的共混物中无定形的PVPh分子分散在P(HB-co-HV)片晶之间与非晶的P(HB-co-HV)分子形成非晶区,从而使非晶区加宽,长周期增加。     

On the interaction of dipalmitoyl phosphatidylcholine with normal long-chain alcohols in a mixed monolayer: a thermodynamic study

This study investigated the mixed monolayer behavior of dipalmitoyl phosphatidylcholine (DPPC) with normal long-chain alcohols at the air/water interface. Surface pressure–area isotherms of mixed DPPC/C₁₈OH and DPPC/C₂₀OH monolayers at 37°C were obtained and compared with previous results for the mixed DPPC/C₁₆OH system. The negative deviations from additivity of the areas and the variation of the collapse pressure with composition imply that DPPC and long-chain alcohols were miscible and formed non-ideal monolayers at the interface. At lower surface pressures, it seems that the attractive intermolecular force was dominant in molecular packing in the mixed monolayers. At higher surface pressures, the data suggest that the molecular packing in mixed DPPC/C₁₆OH monolayers may be favored by the packing efficiency or geometric accommodation. Furthermore, negative values of excess free energy of mixing were obtained and became significant as the hydrocarbon chain length of alcohols increased, which indicates there were attractive interactions between DPPC and long-chain alcohols. In each free energy of mixing–composition curve, there was only one minimum and thus a phase separation did not exist for mixed DPPC/long-chain alcohol monolayers.