An intimate polycarbonate/poly(methyl methacrylate)/poly(vinyl acetate) ternary blend via coalescence from their common inclusion compound with γ‐cyclodextrin

In this study, we successfully report an intimate ternary blend system of polycarbonate (PC)/poly(methyl methacrylate) (PMMA)/poly(vinyl acetate) (PVAc) obtained by the simultaneous coalescence of the three guest polymers from their common γ‐cyclodextrin (γ‐CD) inclusion compound (IC). The thermal transitions and the homogeneity of the coalesced ternary blend were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The observation of a single, common glass transition strongly suggests the presence of a homogeneous amorphous phase in the coalesced ternary polymer blend. This was further substantiated by solid‐state ¹³C NMR observation of the T_1ρ(¹H)s for each of the blend components. For comparison, ternary blends of PC/PMMA/PVAc were also prepared by traditional coprecipitation and solution casting methods. TGA data showed a thermal stability for the coalesced ternary blend that was improved over the coprecipitated blend, which was phase‐segregated. The presence of possible interactions between the three polymer components was investigated by infrared spectroscopy (FTIR). The analysis indicates that the ternary blend of these polymers achieved by coalescence from their common γ‐CD–IC results in a homogeneous polymer blend, possibly with improved properties, whereas coprecipitation and solution cast methods produced phase separated polymer blends. It was also found that control of the component polymer molar ratios plays a key role in the miscibility of their coalesced ternary blends. Coalescence of two or more normally immiscible polymers from their common CD–ICs appears to be a general method for obtaining well‐mixed, intimate blends. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4182–4194, 2004     

Glass‐transition temperatures of nanostructured amorphous bulk polymers and their blends

Nanostructured amorphous bulk polymer samples were produced by processing them with small molecule hosts. Urea (U) and gamma‐cyclodextrin (γ‐CD) were utilized to form crystalline inclusion compounds (ICs) with low and high molecular weight as‐received (asr‐) poly(vinyl acetate) (PVAc), poly(methyl methacrylate) (PMMA), and their blends as included guests. Upon careful removal of the host crystalline U and γ‐CD lattices, nanostructured coalesced (c‐) bulk PVAc, PMMA, and PVAc/PMMA blend samples were obtained, and their glass‐transition temperatures, T_gs, measured. In addition, non‐stoichiometric (n‐s)‐IC samples of each were formed with γ‐CD as the host. The T_gs of the un‐threaded, un‐included portions of their chains were observed as a function of their degree of inclusion. In all the cases, these nanostructured PVAc and PMMA samples exhibited T_gs elevated above those of their as‐received and solution‐cast samples. Based on their comparison, several conclusions were reached concerning how their molecular weights, the organization of chains in their coalesced samples, and the degree of constraint experienced by un‐included portions of their chains in (n‐s)‐γ‐CD‐IC samples with different stoichiometries affect their chain mobilities and resultant T_gs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1041–1050     

Reorganization of the structures,morphologies, and conformations of bulk polymers via coalescence from polymer–cyclodextrin inclusion compounds

Bulk poly(ethylene terephthalate) (PET) and bisphenol A polycarbonate (PC) samples have been produced by the coalescence of their segregated, extended chains from the narrow channels of the crystalline inclusion compounds (ICs) formed between the γ‐cyclodextrin (CD) host and PET and PC guests, which are reported for the first time. Differential scanning calorimetry, Fourier transform infrared, and X‐ray observations of PET and PC samples coalesced from their crystalline γ‐CD‐ICs suggest structures and morphologies that are different from those of samples obtained by ordinary solution and melt processing techniques. For example, as‐received PC is generally amorphous with a glass‐transition temperature (T_g) of about 150 °C; when cast from tetrahydrofuran solutions, PC is semicrystalline with a melting temperature (T_m) of about 230 °C; and after PC/γ‐CD‐IC is washed with hot water for the removal of the host γ‐CD and for the coalescence of the guest PC chains, it is semicrystalline but has an elevated T_m value of about 245 °C. PC crystals formed upon the coalescence of highly extended and segregated PC chains from the narrow channels in the γ‐CD host lattice are possibly more chain‐extended and certainly more stable than chain‐folded PC crystals grown from solution. Melting the PC crystals formed by coalescence from PC/γ‐CD‐IC produces a normal amorphous PC melt that, upon cooling, results in typical glassy PC. PET coalesced from its γ‐CD‐IC crystals, although also semicrystalline, displays a T_m value only marginally elevated from that of typical bulk or solution‐crystallized PET samples. However, after the melting of γ‐CD‐IC‐coalesced PET crystals, it is difficult to quench the resultant PET melt into the usual amorphous PET glass, characterized by a T_g value of about 80 °C. Instead, the coalesced PET melt rapidly recrystallizes during the attempted quench, and so upon reheating, it displays neither a T_g nor a crystallization exotherm but simply remelts at the as‐coalesced T_m. This behavior is unaffected by the coalesced PET sample being held above T_m for 2 h, indicating that the extended, unentangled nature of the chains in the noncrystalline regions of the coalesced PET are not easily converted into the completely disordered, randomly coiled, entangled melt. Apparently, the highly extended, unentangled characters of the PC and PET chains in their γ‐CD‐ICs are at least partially retained after they are coalesced. Initial differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared, and X‐ray observations are described here. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 992–1012, 2002     

Pyrolysis mass spectrometry analysis of polycarbonate/poly(methyl methacrylate)/poly(vinyl acetate) ternary blends

Direct insertion probe pyrolysis mass spectrometry (DIP-MS) analyses of polycarbonate/poly(methyl methacrylate)/poly(vinyl acetate), (PC/PMMA/PVAc), ternary blends have been performed. The PC/PMMA/PVAc ternary blends were obtained by coalescing from their common γ-cyclodextrin-inclusion compounds (CD-ICs), through the removal of the γ-CD host (coalesced blend), and by a co-precipitation method (physical blend). The coalesced ternary blend showed different thermal behaviors compared to the co-precipitated physical blend. The stability of PC chains decreased due to the reactions of CH₃COOH formed by deacetylation of PVAc above 300 °C, for both coalesced and physical blends. This process was more effective for the physical blend most likely due to the enhanced diffusion of CH₃COOH into the amorphous PC domains, where it can further react producing low molecular weight PC fragments bearing methyl carbonate chain ends. The decrease in thermal stability of PC chains was less significant for the coalesced ternary blend indicating that the diffusion of CH₃COOH was either somewhat limited or competed with intermolecular reactions between PMMA and PC and between PMMA and PVAc, which were detected and were associated with their close proximity in the intimately mixed coalesced PC/PMMA/PVAc ternary blend.     

Interactions and prediction of phase diagrams in ternary blends comprising poly(vinyl acetate), poly(vinyl p‐phenol), and poly(methyl methacrylate)

This study investigated and discovered a new miscible ternary blend system comprising three amorphous polymers: poly(vinyl acetate) (PVAc), poly(vinyl p‐phenol) (PVPh), and poly(methyl methacrylate) (PMMA) using thermal analysis and optical and scanning electron microscopies. The ternary compositions are largely miscible except for a small region of borderline ternary miscibility near the side, where the binary blends of PVAc/PMMA are originally of a borderline miscibility with broad T_g. In addition to the discovering miscibility in a new ternary blend, another objective of this study was to investigate whether the introduction of a third polymer component (PVPh) with hydrogen bonding capacity might disrupt or enhance the metastable miscibility between PVAc and PMMA. The PVPh component does not seem to exert any “bridging effect” to bring the mixture of PVAc and PMMA to a better state of miscibility; neither does the Δχ effect seem to disrupt the borderline miscible PVAc/PMMA blend into a phase‐separated system by introducing PVPh. Apparently, the ternary is able to remain in as a miscible state as the binary systems owing to the fact that PVPh is capable of maintaining roughly equal H‐bonding interactions with either PVAc or PMMA in the ternary mixtures to maintain balanced interactions among the ternary mixtures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1147–1160, 2006     

Thermal degradation of polycarbonate, poly(vinyl acetate) and their blends

We have recently developed a novel approach for intimately mixing thermodynamically incompatible polymers, which utilizes the formation of inclusion compounds (ICs) formed with host cyclodextrins (CDs), followed by removal of CD and coalescence of the common guest polymers into a blend. In this paper direct insertion probe pyrolysis mass spectrometry (DIP-MS) analyses of polycarbonate (PC), poly(vinyl acetate) (PVAc) and PC/PVAc blends, obtained by coalescence from their inclusion compounds formed with host γ-CD (coalesced blend) and by co-precipitation (physical blend), have been performed. Variations in the thermal stabilities of the coalesced polymers were recorded both by TGA and DIP-MS and compared to the corresponding as-received polymers. It has been determined that for both coalesced and physical blends of PC/PVAc, CH₃COOH formed by deacetylation of PVAc above 300 °C, reacts with PC chains decreasing their thermal stability. This process was more effective for the physical blend, most likely due to enhanced diffusion of CH₃COOH, produced by deacetylation of PVAc, into the PC domains, where it can further react producing low molecular weight PC fragments bearing methyl carbonate chain ends.     

Organizational stabilities of bulk neat and well‐mixed,blended polymer samples coalesced from their crystalline inclusion compounds formed with cyclodextrins

Cyclodextrins (CDs) are cyclic starches containing α‐1,4‐linked glucose units. Commonly available α‐, β‐, and γ‐CDs have six, seven, and eight glucose units, respectively. They are well known for forming noncovalent inclusion complexes (ICs) with a variety of guest molecules, including many polymers, by threading and inclusion into their relatively hydrophobic interior cavities, which are roughly cylindrical, with diameters of ～0.5–1.0 nm. Warm water washing of crystalline CD‐ICs containing polymer guests insoluble in water or treatment with amylase enzymes serve to remove the host CDs and result in the coalescence of the guest polymers into solid bulk samples. When guest polymers are coalesced from their CD‐ICs by carefully removing the host CD lattices, they are observed to solidify with structures, morphologies, and even conformations that are distinct from bulk samples made from their solutions and melts. In addition, molecularly mixed, intimate blends can be obtained upon coalescence of two or more normally immiscible polymer guests from their common CD‐ICs. Not only are the organizations and behaviors of bulk polymer samples significantly modified on coalescence from their CD‐ICs, but both are also maintained for significant periods of time even when heated above their T_gs and T_ms, where their chains are mobile. Here, we discuss the long‐time, high temperature stabilities of the organizations and properties of bulk polymers coalesced from their crystalline CD‐ICs. While random‐coiling of their initially coalesced, largely extended, separated, and unentangled chains may be relatively rapid, we conclude that the subsequent slow establishment of homogeneous melts or phase‐segregated blends results from the extremely sluggish center‐of‐mass diffusion that must accompany full entanglement of their chains. Apparently, the process of entangling the largely separated and not fully interpenetrating randomly coiled chains initially coalesced from their CD‐ICs is particularly slow, much slower in fact than the center‐of mass diffusion of polymer chains in their fully entangled melts. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1543–1553, 2009     

Unique morphological and thermal behaviors of reorganized poly(ethylene terephthalates)

Bulk poly(ethylene terephthalate) PET has been reorganized both morphologically and conformationally by processing from its inclusion complex (IC) formed with γ‐cyclodextrin (CD). In the narrow channels of its γ‐CD‐IC crystals the included guest PET chains are isolated from neighboring PET chains and the ethylene glycol (EG) units adopt the highly extended g±tg? kink conformations, whose cross‐sectional diameters are ～80% of the diameter of the fully extended, all‐trans crystalline PET conformer, though they are nearly (～95%) as extended. When the highly extended, unentangled guest PET chains are coalesced from their γ‐CD‐IC crystals by exposure to hot water, host γ‐CDs are removed and the PET chains are presumably consolidated into a bulk sample with a morphology and constituent chain conformations not normally found in PET samples solidified from their randomly coiling, possibly entangled, disordered melts and solutions. Observations by polarized light and atomic force microscopies provide visual evidence for widely different semicrystalline morphologies developed in coalesced and as‐received PETs when crystallized from their melts, with possibly chain extended, small crystals and spherulitic, chain‐folded, large crystals, respectively. DSC observations reveal that coalesced PET is rapidly crystallizable from the melt, while as‐received PET is slow to crystallize and is easily quenched into a totally amorphous sample. Analyses of ¹³C‐NMR data strongly indicate that the PET chains in the noncrystalline regions of the coalesced sample remain predominantly in the highly extended kink conformations, with g±tg? EG units, which are required by their inclusion into PET‐γ‐CD‐IC crystals, while the predominantly amorphous PET chains in the as‐received sample have high concentrations of gauche± ? CH₂? CH₂? and trans ? O? CH₂? ,? CH₂? O? EG bond conformations. ¹³C‐NMR T₁(¹³C) and T_1ρ(¹H) relaxation studies show no evidence of a glass transition for coalesced PET, while the as‐received sample shows abrupt changes in both the MHz [T₁(¹³C)] and kHz [T_1ρ(¹H)] motions at T ～ T_g. Preliminary observations of differences in their macroscopic properties are attributed to the very different morphologies and conformations of the constituent chains in these PET samples. Apparently the kink conformers in the noncrystalline regions of coalesced PET are at least partially retained for extended periods even in the melt and are rapidly crystallized upon cooling. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 386–394, 2004     

Development and characterization of reactive extruded PVC/polyacrylate blends

This paper describes a method to obtain polymer blends by the absorption of a liquid solution of monomer, initiator, and a crosslinking agent in suspension type porous poly(vinyl chloride) (PVC) particles, forming a dry blend. These PVC/monomer dry blends are reactively polymerized in a twin‐screw extruder to obtain the in situ polymerization in a melt state of various blends: PVC/poly(methyl methacrylate) (PVC/PMMA), PVC/poly(vinyl acetate) (PVC/PVAc), PVC/poly(butyl acrylate) (PVC/PBA) and PVC/poly(ethylhexyl acrylate) (PVC/PEHA). Physical PVC/PMMA blends were produced, and the properties of those blends are compared to reactive blends of similar compositions. Owing to the high polymerization temperature (180°C), the polymers formed in this reactive polymerization process have low molecular weight. These short polymer chains plasticize the PVC phase reducing the melt viscosity, glass transition and the static modulus. Reactive blends of PVC/PMMA and PVC/PVAc are more compatible than the reactive PVC/PBA and PVC/PEHA blends. Reactive PVC/PMMA and PVC/PVAc blends are transparent, form single phase morphology, have single glass transition temperature (T_g), and show mechanical properties that are not inferior than that of neat PVC. Reactive PVC/PBA and PVC/PEHA blends are incompatible and two discrete phases are observed in each blend. However, those blends exhibit single glass transition owing to low content of the dispersed phase particles, which is probably too low to be detected by dynamic mechanical thermal analysis (DMTA) as a separate T_g value. The reactive PVC/PEHA show exceptional high elongation at break (～90%) owing to energy absorption optimized at this dispersed particle size (0.2–0.8 µm). Copyright © 2005 John Wiley & Sons, Ltd.     

Formation of crystalline inclusion compounds of poly (vinyl chloride) of different stereoregularity with γ-cyclodextrin

This work reports the formation and detailed characterization of the γ-cyclodextrin (γ-CD) inclusion compounds (ICs) formed with two poly (vinyl chloride) samples with different isotactic content. The ICs were characterized by X-ray diffraction, solid state ¹³C-NMR, solution ¹H-NMR, FT-infrared, differential scanning calorimetry, and thermogravimetric analysis. Experimental evidence of the inclusion of the guest polymer chains into the narrow channels created by the γ-CD crystalline host lattice has been obtained. Examination of coalesced poly (vinyl chlorides) (PVCs) obtained after the host γ-CD is removed reveals different characteristics specifically for the coalesced PVC sample with higher isotactic content. An increase in T_g was observed by DSC for this PVC. To the contrary, the T_g of the coalesced PVC sample with lower isotactic content is almost the same as that of the as-synthesized sample. Thermogravimetric analysis indicated that coalesced PVC with higher isotactic content acquires a degree of stabilization after modification by threading into and being extracted from its γ-CD IC. The results suggest that an irreversible conformational change takes place when PVC forms ICs with a solid host lattice like γ-CD. The PVC molecules extend and reorganize into a more stable conformation in the IC, consequently improving the properties of the coalesced sample. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2503–2513, 2007     

Miscibility and ferroelectric behavior in blends of poly(vinylidene fluoride/trifluoroethylene) and poly(vinyl acetate)

The blend system containing a poly(vinylidene fluoride/trifluoroethylene) [P(VDF/TrFE)] copolymer (68/32 mol %) and poly(vinyl acetate) (PVAc) was miscible from the results of differential scanning calorimetry (DSC) studies that exhibit the presence of a single, composition‐dependent glass transition temperature (T_g) and a strong melting point depression for the semicrystalline P(VDF/TrFE) component. However, differences between the DSC and dielectric measurements, which showed a separate P(VDF/TrFE) T_g peak, suggests that the P(VDF/TrFE)/PVAc blends are actually partially miscible. Because of the lower dielectric constant of PVAc and the reduced sample crystallinity caused by the addition of PVAc, both the dielectric constant and the remanent polarization of the copolymer blends decrease with increasing PVAc content. The presence of a small amount of PVAc stabilized the anomalous ferroelectric behavior of ice–water‐quenched P(VDF/TrFE), and the blend portrayed normal polarization reversal behavior after adding only 1 wt % PVAc. The piezoelectric response suggests small changes with an increasing number of poling cycles. It is believed that PVAc affects the D‐E hysteresis behavior at the interface between crystalline and amorphous phases, although much work remains to be done to confirm this hypothesis. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 927–935, 2003     

Pyrolysis mass spectrometry analysis of poly(vinyl acetate), poly(methyl methacrylate) and their blend coalesced from inclusion compounds formed with γ-cyclodextrin

Direct insertion probe pyrolysis mass spectrometry (DIP-MS) analyses of poly(methyl methacrylate) (PMMA), poly(vinyl acetate) (PVAc) and binary PMMA/PVAc guests, coalesced from their inclusion compounds (ICs) formed with host γ-cyclodextrin (γ-CD) through removal of the γ-CD host, have been performed. A slight increase in the thermal stabilities of the coalesced polymers were recorded both by TGA and DIP-MS compared to the corresponding as-received polymers. The DIP-MS observations pointed out that the thermal stability and degradation products of these polymers are affected once they are included inside the IC channels created by the stacked host γ-CDs. DIP-MS observations suggested that the degradation mechanisms for PMMA and PVAc chains in their coalesced blend were significantly altered from those observed in their as-received and solution blended samples. This was attributed to the presence of specific molecular interactions between the intimately mixed PMMA and PVAc chains in their coalesced blend.     

Molecular mixing of incompatible polymers through formation of and coalescence from their common crystalline cyclodextrin inclusion compounds

We describe the successful mixing of polymer pairs and triplets that are normally incompatible to form blends that possess molecular‐level homogeneity. This is achieved by the simultaneous formation of crystalline inclusion compounds (ICs) between host cyclodextrins (CDs) and two or more guest polymers, followed by coalescing the included guest polymers from their common CD–ICs to form blends. Several such CD–IC fabricated blends, including both polymer1/polymer2 binary and polymer1/ polymer2/polymer3 ternary blends, are described and examined by means of X‐ray diffraction, differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, and solid‐state NMR to probe their levels of mixing. It is generally observed that homogeneous blends with a molecular‐level mixing of blend components is achieved, even when the blend components are normally immiscible by the usual solution and melt blending techniques. In addition, when block copolymers composed of inherently immiscible blocks are coalesced from their CD–ICs, significant suppression of their normal phase‐segregated morphologies generally occurs. Preliminary observations of the thermal and temporal stabilities of the CD–IC coalesced blends and block copolymers are reported, and CD–IC fabrication of polymer blends and reorganization of block copolymers are suggested as a potentially novel means to achieve a significant expansion of the range of useful polymer materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4207–4224, 2004     

Synthesis of poly[(2‐oxo‐1,3‐dioxolane‐4‐yl) methyl methacrylate‐co‐ethyl acrylate] by incorporation of carbon dioxide into epoxide polymer and the miscibility behavior of its blends with poly(methyl methacrylate) or poly(vinyl chloride)

This study was related to the investigation of the chemical fixation of carbon dioxide to a copolymer bearing epoxide and the application of the cyclic carbonate group containing copolymer‐to‐polymer blends. In the synthesis of poly[(2‐oxo‐1,3‐dioxolane‐4‐yl) methyl methacrylate‐co‐ethyl acrylate] [poly(DOMA‐co‐EA)] from poly(glycidyl methacrylate‐co‐ethyl acrylate) [poly(GMA‐co‐EA)] and CO₂, quaternary ammonium salts showed good catalytic activity. The films of poly(DOMA‐co‐EA) with poly(methyl methacrylate) (PMMA) or poly(vinyl chloride) (PVC) blends were cast from N,N′‐dimethylformamide solution. The miscibility of the blends of poly(DOMA‐co‐EA) with PMMA or PVC have been investigated both by DSC and visual inspection of the blends. The optical clarity test and DSC analysis showed that poly(DOMA‐co‐EA) containing blends were miscible over the whole composition range. The miscibility behaviors were discussed in terms of Fourier transform infrared spectra and interaction parameters based on the binary interaction model. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1472–1480, 2001     

Synthesis of poly[(2‐oxo‐1,3‐dioxolane‐ 4‐yl)methyl methacrylate‐co‐styrene] by addition reaction of carbon dioxide and its compatibility with poly(methyl methacrylate) or poly(vinyl chloride)

We investigated the chemical fixation of carbon dioxide (CO ₂) to a copolymer bearing epoxide and the application of the cyclic carbonate group containing copolymer to polymer blends. In the synthesis of poly[(2‐oxo‐1,3‐dioxolane‐4‐yl)methyl methacrylate‐co‐styrene] [poly(DOMA‐co‐St)] from the addition of CO ₂ to poly(glycidyl methacrylate‐co‐styrene) [poly(GMA‐co‐St)], quaternary ammonium salts showed good catalytic activity at mild reaction conditions. The CO ₂ addition reaction followed pseudo first‐order kinetics with the concentration of poly(GMA‐co‐St). In order to expand the applications of the CO ₂ fixed copolymer, polymer blends of this copolymer with poly(methyl methacrylate) (PMMA) or poly(vinyl chloride) (PVC) were cast from N,N′‐dimethylformamide (DMF) solution. Miscibility of blends of poly(DOMA‐co‐St) with PMMA or PVC have been investigated both by differential scanning calorimetry (DSC) and visual inspection of the blends, and the blends were miscible over the whole composition ranges. The miscibility behaviors were also discussed in terms of FT‐IR spectra. Copyright © 2002 John Wiley & Sons, Ltd.     

Inclusion Compounds Formation of Poly(azomethine ether)s and β‐Cyclodextrin

In this study, two poly(azomethine ether)s were synthesized and they can form inclusion compounds (ICs) with β‐cyclodextrin (β‐CD). Fourier transform infrared (FTIR) spectroscopy, ¹H nuclear magnetic resonance spectroscopy (¹H‐NMR), thermogravimetric analysis (TGA), X‐ray diffraction (XRD) have been utilized to observe the formation of polymer‐CD‐ICs. The differentiation in their FTIR spectra may indicate the formation of the inclusion compounds between poly(azomethine ether)s and β‐CD. Compared the ¹H‐NMR of polymer‐CD‐ICs with β‐CD, proton signals belonging to both β‐CD and poly(azomethine ether)s can be found in the spectrum. The chemical shift of the protons H‐3, H‐5 has changed after the formation of inclusion compounds, which is perhaps due to the interaction of these protons with polymers. TGA scans showed the much higher decomposition temperatures observed for two polymer‐CD‐ICs may imply that polymer chains included inside the β‐CD's cavity can greatly improve β‐CD's stabilities. The X‐ray diffraction patterns were confirmed to be the new crystal structures.     

STUDIES OF THE CRYSTALLIZATION BEHAVIOR IN THE CRYSTALLINE/AMORPHOUS POLYMER BLENDS: POLY(ETHYLENE OXIDE)/POLY(METHYL METHACRYLATE) AND POLY(ETHYLENE OXIDE)/POLY(VINYL ACETATE)

The crystallization process of poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA)and PEO/poly(vinyl acetate) (PVAc) blends has been characterized by Fourier Transform Infrared(FTIR) spectra in conjunction with Differential Scanning Calorimeter (DSC) measurements. Thecrystallinity of PEO varies consistently with PEO content in PEO/PVAc blends and the PEO/PMMAblends containing 50 wt% or less PMMA. For the PEO/PMMA blends containing 60 wt% ormore PMMA, the crystallinity of PEO decreases more than PEO content but develops with crystal-lization time. These results can be explained in terms of difference between the crystallization tem-perature (T_c) and glass transition temperature (T_g) of the blends as a function of content of amorphouscomponent.     

Investigation at the chain segmental level of the miscibility of poly(vinyl chloride)/atactic poly(methyl methacrylate) blends

We employed high‐resolution ¹³C cross‐polarization/magic‐angle‐spinning/dipolar‐decoupling NMR spectroscopy to investigate the miscibility and phase behavior of poly(vinyl chloride) (PVC)/poly(methyl methacrylate) (PMMA) blends. The spin–lattice relaxation times of protons in both the laboratory and rotating frames [T₁(H) and T_1ρ(H), respectively] were indirectly measured through ¹³C resonances. The T₁(H) results indicate that the blends are homogeneous, at least on a scale of 200–300 Å, confirming the miscibility of the system from a differential scanning calorimetry study in terms of the replacement of the glass‐transition‐temperature feature. The single decay and composition‐dependent T_1ρ(H) values for each blend further demonstrate that the spin diffusion among all protons in the blends averages out the whole relaxation process; therefore, the blends are homogeneous on a scale of 18–20 Å. The microcrystallinity of PVC disappears upon blending with PMMA, indicating intimate mixing of the two polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2390–2396, 2001     

Blends of polycarbonate and poly(ϵ‐caprolactone) and the determination of the polymer–polymer interaction parameter of the two polymers

The thermal properties of blends of polycarbonate (PC) and poly(ε‐caprolactone) (PCL) were investigated by differential scanning calorimetry (DSC). From the thermal analysis of PC‐PCL blends, a single glass‐transition temperature (T_g) was observed for all the blend compositions. These results indicate that there is miscibility between the two components. From the modified Lu and Weiss equation, the polymer–polymer interaction parameter (χ₁₂) of the PC‐PCL blends was calculated and found to range from −0.012 to −0.040 with the compositions. The χ₁₂ values calculated from the T_g method decreased with the increase of PC weight fraction. By taking PC‐PCL blend as a model system, the values of χ₁₂ were compared with two different methods, the T_g method and melting point depression method. The two methods are in reasonably good agreement for the χ₁₂ values of the PC‐PCL blends. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2072–2076, 2000     

Mechanical properties and morphology of epoxy/poly(vinyl acetate)/poly(4-vinyl phenol) brominated system

Diglycidyl ether of bisfenol-A (DGEBA)/poly(vinyl acetate) (PVAc)/poly(4-vinyl phenol) brominated (PVPhBr) ternary blends cured with 4,4’-diaminodiphenylmethane (DDM) were investigated by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM). Homogeneous (DGEBA+DDM)/PVPhBr networks with a unique T _g are generated. Ternary blends (DGEBA+DDM)/PVAc/PVPhBr are initially miscible and phase separate upon curing arising two T _gs that correspond to a PVAc-rich phase and to epoxy network phase. Increasing the PVPhBr content the T _gof the PVAc phase move to higher temperatures as a consequence of the PVAc-PVPhBr interactions. Different morphologies are generated as a function of the blend composition.