Excimer formation in uniaxially stretched polymer films

The steady-state fluorescence properties of naphthalene-labeled polymers dispersed in poly(methyl methacrylate) (PMMA) cast films were studied under tensile loadings at 80 degreesC. The labeled polymers were composed of methyl methacrylate (MMA) and 1-naphthylmethyl methacrylate (NMMA). Three of the copolymers were used in this work, and the contents of NMMA were 0.59 mol % (CP1), 22.0 mol % (CP2), and 56.7 mol % (CP3), respectively. The fluorescence spectra of the films containing CP1 and CP2were unchanged during elongation. For the film containing CP3, the excited monomer emission of naphthyl groups at around 337 nm decreased with increasing applied tensile strain. The strain enhanced the emission ascribed to the excimer of the naphthyl groups in the region of 390-420 nm. The ratio of fluorescence intensities at 400 nm and 337 mn, I-400/I-337, increased with the applied strain, which indicates that CP3 is a sensitive probe for detecting the structural changes of polymer matrices. The obtained results mean that the excimer-forming sites in the PMMA films during elongation depend both on the applied strain and the concentration of naphthyl groups in the dispersed polymer probes. (C) 2001 John Wiley & Sons, Inc.

Thermodynamics of PMMA/SAN blends: Application of the Sanchez-Lacombe lattice fluid theory

Polymer blends of poly(methyl methacrylate) (PMMA) and poly(styrene-co-acrylonitrile) (SAN) with an acrylonitrile content of about 30 wt % were prepared by means of solution-casting and characterized by virtue of pressure-volume-temperature (PVT) dilatometry. The Sanchez-Lacombe (SL) lattice fluid theory was used to calculate the spinodals, the binodals, the Flory-Huggins (FH) interaction parameter, the enthalpy of the mixing, the volume change of the mixing, and the combinatorial and vacancy entropies of the mixing for the PMMA/SAN system. A new volume-combining rule was used to evaluate the close-packed volume per mer, upsilon*, of the PMMA/SAN blends. The calculated results showed that the new and the original volume-combining rules had a slight influence on the FH interaction parameter, the enthalpy of the mixing, and the combinatorial entropy of the mixing. Moreover, the spinodals and the binodals calculated with the SL theory by means of the new volume-combining rule could coincide with the measured data for the PMMA/SAN system with a lower critical solution temperature, whereas those obtained by means of the original one could not.

Theoretical calculation of Flory-Huggins and scattering interaction parameters by means of the lattice fluid theory for PVME/PSD blends

By fitting the spinodals of poly(vinyl methyl ether)/deuterated polystyrene (PVME/PSD) systems, the adjustable parameters epsilon (12)* and delta epsilon* in the Sanchez-Balasz lattice fluid (SBLF) theory could be determined for different molecular weights. According to these parameters, Flory-Huggins and scattering interaction parameters were calculated for PVME/PSD with different molecular weights by means of the SELF theory. From our calculation, Flory-Huggins and scattering interaction parameters are both Linearly dependent on the reciprocal of the temperature, and almost linearly on the concentration of PSD. Compared with the scattering interaction parameters, the Flory-Huggins interaction parameters decreased more slowly with an increase in the concentration for all three series of blends.

Study of elastic modulus and yield strength of polymer thin films using atomic force microscopy

Nanometer-scale elastic moduli and yield strengths of polycarbonate (PC) and polystyrene (PS) thin films were measured with atomic force microscopy (AFM) indentation measurements. By analysis of the AFM indentation force curves with the method by Oliver and Pharr, Young's moduli of PC and PS thin films could be obtained as 2.2 +/- 0.1 and 2.6 +/- 0.1 GPa, respectively, which agree well with the literature values. By fitting Johnson's conical spherical cavity model to the measured plastic zone sizes, we obtained yield strengths of 141.2 MPa for PC thin films and 178.7 MPa for PS thin films, which are similar to2 times the values expected from the literature. We propose that it is due to the AFM indentation being asymmetric, which was not accounted for in Johnson's model. A correction factor, epsilon, of similar to0.72 was introduced to rescale the plastic zone size, whereupon good agreement between theory and experiment was achieved.

Synthesis, crystal structure and reactivity of (2,4-C7H11)(2)Yb center dot DME

(2,4-C7H11)(2)Yb . DME was synthesized by the reaction of YbCl3 with K(2,4-C7H11)(2,4-dimethylpentadienyl potassium), and the single crystal X-ray diffraction showed that the complex exists in a cis- staggered conformation. Thf crystal of the compound belongs to the monoclinic space group P2(1)/n with a = 0.675 2 (1) nm, b = 1.490 6 (1) nm, c = 1.529 3 (2) nm, beta = 97.55 (2)degrees, V = 1.977 79 (4) nm(3), Z = 4, F(000) = 735.8 e, mu = 49.49 cm(-1), R = 0.033 and R-w = 0.032. The title complex can be used as a catalyst for the polymerization of methyl methacrylate (MMA).

Morphology, structure, and rheological property of linear low-density polyethylene grafted with acrylic acid

The chain structure, spherulite morphology, and theological property of LL-DPE-g-AA were studied by using electronspray mass spectroscopy, C-13-NMR, and rheometer. Experimental evidence proved that AA monomers grafted onto the LLDPE backbone formed multiunit AA branch chains. It was found that AA branch chains could hinder movement of the LLDPE main chain during crystallization. Spherulites of LLDPE became more anomalous because of the presence of AA branch chains. Rheological behavior showed that AA branch chains could act as an inner plasticizer at the temperature range of 170-200 degreesC, which made LLDPE-g-AA easy to further process. (C) 2001 John Wiley & Sons, Inc.

Synthesis and luminescence properties of organic-inorganic hybrid thin films doped with Eu(III)

In this study, silica-based transparent organic-inorganic hybrid films were prepared by the sol-gel method. Tetraethoxysilane and 3-(trimethoxysilyl)propyl methacrylate were used as the inorganic and organic compounds, respectively. Lanthanide complexes [Eu(phen)(2)]Cl-3 were incorporated into the organically modified silicates (ORMOSIL) and the luminescence properties of the resultant hybrid films (ORMOSIL:[Eu(phen)(2)]Cl-3) were characterized. The relative quantum efficiency was observed higher and the lifetimes were longer in hybrid films than those in pure silica films. Furthermore, thermal stability of hybrid films incorporating various concentration of Eu(III) complex was studied. (C) 2001 Elsevier Science B.V. All rights reserved.

Efforts to decrease crosslinking extent of polyethylene in a reactive extrusion grafting process

Grafting of acrylic acid and glycidyl methacrylate onto low density polyethylene (LDPE) was performed by using a corotating twin-screw extruder. The effects of residence time and concentration of initiator and monomers on degree of grafting and gel content of grafting LDPE were studied systematically. Paraffin, styrene, p-benzoquinone, triphenyl phosphite, tetrachloromethane, and oleic acid were added to try to decrease the extent of crosslinking of LDPE. 4-hydroxyl-2,2,6,6-tetramethyl-1-piperidinyloxy (4-hydroxyl-TEMPO) and dipentamethylenethiuram tetrasulfide were also tried to inhibit crosslinking reaction of LDPE during its extruding grafting process. It was found that p-benzoquinone, triphenyl phosphite and tetrachloromethane were good inhibitors for crosslinking of LDPE. (C) 2000 John Wiley & Sons, Inc.

Mixing enthalpy and phase behavior of PEO/PVAc blends

Phase behaviors and heats of mixing of the miscible blends of poly(ethylene oxide) (PEO) and poly(vinyl acetate) (PVAc) with different molecular weights were investigated by DSC. A method proposed by Natasohn and Ebert et al. was adopted to estimate the binodal temperatures and the enthalpies of mixing from onset temperatures and values of areas of a series of endothermic peaks (corresponding to heats of demixing), respectively, in their heating scanning thermograms obtained with different heating rates. Phase diagrams and heats of mixing of this blending system were also predicted by using Sanchez-Lacombe lattice fluid theory. A very good agreement was obtained for both. phase behaviors and heats of mixing obtained with two different methods.

Studies on the interfacial adhesion between functionalized polypropylene and polyamide 1010

The interface behavior of polyamide 1010 (PA1010) and polypropylene (PP) was studied. In order to improve their interfacial adhesion, functional PP was prepared by means of grafting glycidyl methacrylate (GMA) on PP main chains and used instead of plain PP. Several technological characterizations were performed here on their interfaces. ESCA was used to confirm that some kind of reaction occurred between end groups of PA1010 and epoxy species of PP-g-GMA. The peel test was adopted to measure interfacial adhesion. It was found that the fracture energy of interfaces between PA1010 and PP-g-GMA was dramatically increased with the content of GMA. Their interfaces were observed as being blurred by using SEM and TEM and a crack that could be seen in the case of the interfaces of the PA1010 and the plain PP disappeared.

Monte Carlo simulation of phase separation of A/B/A-B ternary mixtures

Monte Carlo simulations were used to model A/B/A-B ternary mixtures with different AB diblock copolymer volume fractions for which both the dispersed and continuous phase volume fractions were kept constant. For concentrations of the diblock copolymer below a critical value, the domain size increment of the dispersed phase decreases linearly with the copolymer concentration. This is in agreement with the predictions of Noolandi and Hong. The dependence of the domain size as a function of the copolymer volume fraction can also be fitted by the equation of Tang and Huang. Our simulations indicate, for the first time, that the micelles form before saturation of the interface occurs. This means that the formation of the micelles is not a result of the saturation of the interface.

Rheological, thermal, and morphological properties of ABS-PA1010 blends

Noncompatibilized and compatibilized ABS-nylon1010 blends were prepared by melt mixing. Polystyrene and glycidyl methacrylate (SG) copolymer was used as a compatibilizer to enhance the interfacial adhesion and to control the morphology. This SG copolymer contains reactive glycidyl groups that are able to react with PA1010 end groups (-NH2 or -COOH) under melt conditions to form SG-g-Nylon copolymer. Effects of the compatibilizer SG on the rheological, thermal, and morphological properties were investigated by capillary rheometer, DSC, and SEM techniques. The compatibilized ABS-PA1010 blend has higher viscosity, lower crystallinity, and smaller phase domain compared to the corresponding noncompatibilized blend. (C) 1999 John Wiley & Sons, Inc.

Studies on blends of LLDPE and polar polymers compatibilized by a random copolymer

Compatibilization of blends of Linear low-density polyethylene (LLDPE)-poly(methyl methacrylate) (PMMA) and LLDPE-copolymer of methyl methacrylate (MMA) and 4-vinylpyridine (poly(MMA-co-4VP) with poly(ethylene-co-methacrylic acid) (EMAA) have been studied. Mechanical properties of the LLDPE-PMMA blends increase upon addition of EMAA. In order to further improve interfacial adhesion of LLDPE and PMMA, 4-vinyl pyridine units are introduced into PMMA chains, or poly(MMA-co-4VP) is used as the polar polymer. In LLDPE-poly(MMA-co-4VP)-EMAA blends, interaction of MAA in EMAA with 4VP of poly(MMA-co-4VP) causes a band shift in the infrared (IR) spectra. Chemical shifts of N-1s binding energy in X-ray photoelectronic spectroscopy (XPS) experiments indicate a transfer of proton from MAA to 4VP. Scanning electron microscopy (SEM) pictures show that the morphology of the blends were improved upon addition of EMAA. Nonradiative energy transfer (NRET) fluorescence results attest that there exists interdiffusion of chromophore-labeled LLDPE chains and chromophore-labeled poly(MMA-co-4VP) chains in the interface. Based on experimental results, the mechanism of compatibilization is studied in detail. Compatibilization is realized through the interaction between MAA in EMAA with 4VP in poly(MMA-co-4VP). (C) 1999 John Wiley & Sons, Inc.

Effect and mechanism in compatibilization of poly(styrene-b-2-ethyl-2-oxazoline) diblock copolymer in poly(2,6-dimethyl-1,4-phenylene oxide) poly(ethylene-ran-acrylic acid) blends

The compatibilization effect of poly(styrene-b-2-ethyl-2-oxazoline) diblock copolymer, P(S-b-EOx), on immiscible blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and poly(ethylene-co-acrylic acid) (EAA) is examined in terms of phase structure and thermal, rheological and mechanical properties, and its compatibilizing mechanism is investigated by Fourier-transform infrared spectroscopy. The block copolymer, synthesized by a mechanism transformation copolymerization, is used in solution blending of PPO/EAA. Scanning electron micrographs show that the blends exhibit a more regular and finer dispersion on addition of a small amount of P(S-b-EOx). Thermal analysis indicates that the grass transition of PPO and the lower endothermic peal; of EAA components become closer on adding P(S-b-EOx), and the added diblock copolymer is mainly located at the interface between the PPO and EAA phases. The interfacial tension estimated by theological measurement is significantly reduced on addition of a small amount of P(S-b-EOx). The tensile strength and elongation at break increase with the addition of the diblock copolymer for PPO-rich blends, whereas the tensile strength increases but the elongation at break decreases for EAA-rich blends. This effect is interpreted in terms of interfacial activity and the reinforcing effect of the diblock copolymer, and it is concluded that the diblock copolymer plays a role as an effective compatibilizer for PPO/EAA blends. The specific interaction between EAA and polar parts of P(S-b-EOx) is mainly hydrogen bonding. (C) 1998 Elsevier Science Ltd. All rights reserved.

Compatibilizing effect of polystyrene-block-poly(4-vinylpyridine) for poly(2,6-dimethyl-1,4-phenyleneoxide) chlorinated polyethylene blends

The compatibilizing effect and mechanism of compatibilization of the diblock copolymer polystyrene-block-poly(4-vinylpyridine) P(S-b-4VPy) on immiscible blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)/chlorinated polyethylene (CPE) were studied by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), mechanical properties and FTIR measurements. The block copolymer was synthesized by sequential anionic polymerization and melt-blended with PPO and CPE. The results show that the P(S-b-4VPy) added acts as an effective compatibilizer, located at the interface between the PPO and the CPE phase, reducing the interfacial tension, and improving the interfacial adhesion. The tensile strength and modulus of all blends increase with P(S-b-4VPy) content, whereas the elongation at break increases for PPO-rich blends, but decreases for CPE-rich blends. The polystyrene block of the diblock copolymer is compatible with PPO, and the poly(4-vinylpyridine) block and CPE are partially miscible.