Miscibility and morphology in crystalline/amorphous blends of poly(caprolactone)/poly(4-vinylphenol) as studied by DSC, FTIR, and C solid state NMR

The miscibility and morphology of poly(caprolactone) (PCL) and poly (4-vinylphenol) (PVPh) blends were investigated by using differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and ¹³C solid state nuclear magnetic resonance (NMR) spectroscopy. The DSC results indicate that PCL is miscible with PVPh. FTIR studies reveal that hydrogen bonding exists between the hydroxyl groups of PVPh and the carbonyl groups of PCL. ¹³C cross polarization (CP)/magic angle spinning (MAS)/dipolar decoupling (DD) spectra of the blends show a 1 ppm downfield shifting of ¹³C resonance of PVPh hydroxyl-substituted carbons and PCL carbonyl carbons with increasing PCL content. Both FTIR and NMR give evidence of inter-molecular hydrogen bonding within the blends. The proton spin-lattice relaxation in the laboratory frame, T₁(H), and in the rotating frame, T_1ρ(H), were studied as a function of the blend composition. The T₁(H) results are in good agreement with thermal analysis; i.e. the blends are completely homogeneous on the scale of 50-80 nm. The T_1ρ(H) results indicate that PCL in the blends has both crystalline and amorphous phases. The amorphous PCL phase is miscible with PVPh, but the PCL crystal domain size is probably larger than the spin-diffusion path length within the T_1ρ(H) time-frame, i.e. larger than 2-4 nm. The mobility differences between the crystalline and amorphous phases of PCL are clearly visible from the T_1ρ(H) data.     

Miscibility enhancement on the immiscible binary blend of poly(vinyl acetate) and poly(vinyl pyrrolidone) with bisphenol A

The miscibility behavior and hydrogen bonding of ternary blends of bisphenol A (BPA)/poly(vinyl acetate) (PVAc)/poly(vinyl pyrrolidone) (PVP) were investigated by using differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). The BPA is miscible with both PVAc and PVP based on the observed single T_g over the entire composition range. FTIR was used to study the hydrogen-bonding interaction between the hydroxyl group of BPA and the carbonyl group of PVAc and PVP at various compositions. Furthermore, the addition of BPA is able to enhance the miscibility of the immiscible PVAc/PVP binary blend and eventually transforms into miscible blend with single T_g, when a sufficiently quantity of the BPA is present due to the significant Δχ and the ΔK effect.     

Study of miscibility of melamine-formaldehyde resin and poly(vinyl acetate) blends for use as adhesives in engineered flooring

The objective of this research was to investigate the miscibility behavior of melamine-formaldehyde (MF) resin and poly(vinyl acetate) (PVAc) blends for their use as adhesives for bonding fancy veneer and plywood in engineered flooring, by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR). Blends of various compositions of MF resin/PVAc were prepared. To determine and compare the effect of PVAc content, blends with PVAc to MF resin weight ratios of 0, 30, 50, 70 and 100% were prepared. These blends displayed a single cure temperature over the entire range of compositions indicating that this blend system was miscible in the amorphous phase due to the formation of hydrogen bonding between the amine groups of the MF resin and the carbonyl groups of PVAc.     

Thermal properties, miscibility and specific interactions in comparison of linear and star poly(methyl methacrylate) blend with phenolic

A series of miscible linear and star poly(methyl methacrylate) (PMMA)/phenolic blends with different compositions have been prepared. T_gs of both systems are negative derivation from the average values, implying that the self-association interaction is stronger than the inter-association interaction between linear or star PMMA with phenolic. The proton spin-lattice relaxation time in the rotating frame (T_1ρ^H) determined by high resolution solid state ¹³C NMR indicates single composition dependent T_1ρ^H from all blends, implying a good miscibility with chain dynamics on a scale of 1-2 nm. However, T_1ρ^Hs of star PMMA/phenolic blends are relatively smaller than those of linear PMMA/phenolic blends, implying that the degree of homogeneity of star PMMA/phenolic blends is higher than those of linear PMMA/phenolic blends. According to FT-IR analyses, the above results can be rationalized that the hydrogen-bonding interaction of the star PMMA/phenolic blends is greater than the corresponding linear PMMA/phenolic blends.     

Miscibility with positive deviation in Tg-composition relationship in blends of poly(2-vinyl pyridine)-block-poly(ethylene oxide) and poly(p-vinyl phenol)

Phase behavior and miscibility with positive deviation from linear T_g-composition relationship in a copolymer/homopolymer blend system, poly(2-vinyl pyridine)-block-poly(ethylene oxide) (P2VP-b-PEO)/poly(p-vinyl phenol) (PVPh), were investigated by differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR) and solid-state ¹³C nuclear magnetic resonance (¹³C NMR), optical microscopy (OM), and scanning electron microscopy (SEM). Optical and electron microscopy results as well as NMR proton spin-lattice relaxation times in laboratory frame () all confirmed the miscibility as judged by the T_g criterion using DSC. In comparison to the literature result on a homopolymer/homopolymer blend of P2VP/PVPh, fitting with the Kwei equation on the T_g-composition relationship for the block-copolymer/homopolymer blend of P2VP-b-PEO/PVPh blend system yielded a smaller q value (q = 120) for P2VP-b-PEO/PVPh than that for P2VP/PVPh blend (q = 160). The FT-IR and ¹³C NMR results revealed hydrogen-bonding interactions between the pendant pyridine group of P2VP-b-PEO and phenol unit in PVPh, which is responsible for the noted positive deviation of the T_g-composition relationship. Comparison of the shifts of hydroxyl IR absorbance band, reflecting the average strength of H-bonding, indicates a decreasing order of P2VP/PVPh > P2VP-b-PEO/PVPh > PEO/PVPh blends. The PEO block in the copolymer segment tends to defray the interaction strength in the P2VP-b-PEO/PVPh blends because of relative weaker interaction between PEO and PVPh than that between P2VP and PVPh pairs. A comparative ternary (P2VP/PEO)/PVPh blend was also studied as the controlling experiments for comparison to the P2VP-b-PEO/PVPh blend. The thermal behavior and interaction strength in (P2VP/PEO)/PVPh ternary blends are discussed with those in the P2VP-b-PEO/PVPh copolymer/homopolymer blend.     

Miscibility and Phase Morphology of MF/PVAc Hybrid Resins for Surface Bonding of Building Interior Materials

The objective of this research was to investigate the miscibility behavior of melamine‐formaldehyde resin and poly(vinyl acetate) blends for use as adhesives for surface materials in order to reduce formaldehyde emission. The investigation was conducted using differential scanning calorimetry, Fourier transform infrared spectroscopy, ¹³C CP/MAS solid state NMR, scanning electron microscope, atomic force microscopy and wide‐angle X‐ray scattering. Blends of various MF resin/PVAc weight compositions, comprising 0, 30, 50, 70 and 100%, were prepared in order to determine and compare the effect of PVAc content. These blends displayed a single cure temperature over the entire range of compositions indicating that this blend system was miscible in the amorphous phase due to the formation of hydrogen bonding between the amine groups of the MF resin and the carbonyl groups of PVAc. On the surface of the cured blends, the homogeneous dispersion of the PVAc phase in the MF resin was evident as small spherical domains and the blends were confirmed to be well combined.

     

Miscibility and intermolecular specific interactions in blends of poly(hydroxyether of bisphenol A) and poly(4-vinyl pyridine)

The blends of poly(hydroxyether of bisphenol A) (phenoxy) with poly(4-vinyl pyridine) (P4VPy) were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and high-resolution solid-state nuclear magnetic resonance (NMR) spectroscopy. The single, composition-dependent glass transition temperature (T_g) was observed for each blend, indicating that the system is completely miscible. The sigmoid T_g-composition relationship is characteristic of the presence of the strong intermolecular specific interactions in the blend system. FTIR studies revealed that there was intermolecular hydrogen bonding in the blends and the intermolecular hydrogen bonding between the pendant hydroxyl groups of phenoxy and nitrogen atoms of pyridine ring is much stronger than that of self-association in phenoxy. To examine the miscibility of the system at the molecular level, the high resolution ¹³C cross-polarization (CP)/magic angle spinning (MAS) together with the high-power dipolar decoupling (DD) NMR technique was employed. Upon adding P4VPy to the system, the chemical shift of the hydroxyl-substituted methylene carbon resonance of phenoxy was observed to shift downfield in the ¹³C CP/MAS spectra. The proton spin-lattice relaxation time T₁(H) and the proton spin-lattice relaxation time in the rotating frame T_1ρ(H) were measured as a function of the blend composition. In light of the proton spin-lattice relaxation parameters, it is concluded that the phenoxy and P4VPy chains are intimately mixed on the scale of 20-30 Å.     

The effect of chain length of flexible diacid on morphology and mechanical property of modified phenolic resin

Adipic acid (DA4), suberic acid (DA6), sebacic acid (DA8), and dodecanedioic acid (DA10) were used to improve the brittleness of resol type phenolic resin (PF). Chemical reaction of PF with diacid was manifested by a shift of carbonyl stretching peak of diacid to a higher frequency in FT-IR spectra. The modified PF with diacid showed an optimum content (0.0014 mol) and an optimum chain length of diacid (n=6, i.e. DA6) to improve effectively its brittleness. The highly cured phenolic resins with DA4 and DA6 were found to have homogeneous morphologies, but those with DA8 and DA10 had phase-separated morphologies in scanning electron microscopy (SEM) images. The slightly cured PFs with DA4, DA8, and DA10 exhibited phase-separated morphologies, but that with DA6, a homogeneous morphology on SEM micrographs. Furthermore, the latter was confirmed by a proton spin-lattice relaxation time (T₁^H) measurement on solid-state ¹³C NMR spectra. It was found by X-ray diffraction and differential scanning calorimeter that the phase-separated part of modified phenolic resin was a crystalline phase of unreacted diacid. The highly improved toughness of modified PF with DA6 was attributed to the inherently homogeneous morphology with domain sizes around 20-30 nm scale found by the T₁^H measurement.     

Miscibility of Crystalline/Amorphous/Crystalline Biopolymer Blends from PLLA/PDLLA/PHB with Additives

Miscibility of three biopolymers (PLLA, PDLLA and PHB) blends were investigated by POM, WAXD, FTIR, and DSC. DSC verified the thermal properties of biopolymer blend with PVAc as a compatibilizer, and TBC as plasticizer. Some change in glass transition temperature (T_g) of biopolymer blends from 60°C to 0.7°C. The spherulitic morphology of blend 9 changing by addition more PHB (50%), the results dendritic spherulites. The adding PHB to PLLA blends make certain shifting in the diffraction peak from 2 ? = 16.9° to 2 ? = 16.6° and the carbonyl group shifts from 1752 cm^?1 to 1732 cm^?1 in blends, demonstrating polar interactions between them.     

Mechanical properties, morphology and molecular characteristics of poly(ethylene terephthalate) toughened by natural rubber

The melt blending of poly(ethylene terephthalate) (PET) and natural rubber (NR) in a twin-screw extruder is studied. Parameters affecting the blend properties such as the amounts of the NR in the blends and screw speeds are investigated. Increased toughness of the PET/NR blend was found as the amount of NR was increased. The impact strength of the PET/NR (80/20 wt%) blend using a screw speed of 100 rpm, increased up to seven-fold when compared to that of pure PET. The morphology of the blend was investigated by SEM. The molecular characteristic was evaluated by spectroscopic technique. The toughening effect of NR on the PET might come from the possible interaction between the two phases, which was clearly evidenced by solid-state CP/MAS ¹³C NMR data. The data revealed an increase in the cross polarization time (T_D) of the carbonyl carbon and a decrease of the relaxation of the carbonyl groups in the PET/NR blend. This should come from the interaction between the carbonyl group of PET with some abnormal groups such as hydroxyl function in the NR, resulting in an improvement of the compatibility of the studied blends.     

Interactions in miscible blends and complexes of poly(N-acryloylmorpholine) with poly(p-vinylphenol)

Poly(p-vinylphenol) (PVPh) and poly(N-acryloylmorpholine) (PAcM) form interpolymer complexes in ethanol/water (1:1) solution. However, only ordinary blends are obtained from dimethylformamide solution. Each of the complexes and ordinary blends shows one composition-dependent glass transition temperature, indicating its single-phase nature. Fourier transform infrared spectroscopy and ¹³C solid-state nuclear magnetic resonance spectroscopy reveal the existence of hydrogen-bonding interactions between the hydroxyl groups of PVPh and the carbonyl groups as well as the ether oxygen of PAcM in the blends and complexes. In addition, X-ray photoelectron spectroscopy shows that the nitrogen atoms in PAcM are also involved in hydrogen-bonding interactions. Measurements of proton spin-lattice relaxation time in the rotating frame, T_1ρ(H), reveal that each of the complexes and ordinary miscible blends has one composition-dependent T_1ρ(H), indicating an intimate mixing on a scale of about 1.5 nm. The blends show a higher degree of surface enrichment of PVPh than the complexes.     

Comparison of hydrogen bonding interaction between PMMA/PMAA blends and PMMA-co-PMAA copolymers

A series of miscible PMMA/PMAA blends and PMMA-co-PMAA copolymers with different compositions were prepared in this study. T_gs of PMMA-co-PMAA copolymers are significantly higher than average values or from the Fox equation. The proton spin-lattice relaxation time in the rotating frame (T_1ρ^H) determined by high resolution solid state ¹³C nuclear magnetic resonance indicates single composition-dependent from all blends and copolymers, implying a good miscibility with chain dynamics on a scale of 1-2 nm. However, T_1ρ^Hs of copolymers are still smaller than those of blends, implying that degrees of homogeneity of copolymers are higher than those of blends. On the basis of Kovacs' free volume theory, the free volume of the copolymer obtained is decreased which is another indication of greater homogeneity of the copolymer than that of the corresponding blend. According to Fourier transform infrared spectroscopy analyses, the above results can be rationalized that the hydrogen bonding interaction of the copolymer is stronger than the blend.     

Miscibility and phase behavior in blends of phenolphthalein poly(ether sulfone) and poly(hydroxyether of bisphenol A)

Miscibility and phase behavior in the blends of phenolphthalein poly(ether sulfone) (PES-C) with poly(hydroxyether of bisphenol A) (PH) were investigated by means of differential scanning calorimetry (DSC), high resolution solid state nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FTIR). It was found that the homogeneity of the as-prepared blends depended on the solvents used; N,N-dimethylformamide (DMF) provided the segmental mixing for PH and PES-C, which is confirmed by the behavior of single, composition-dependent glass transition temperatures (T_g's). To examine the homogeneity of the blends at the molecular level, the proton spin-lattice relaxation times in the rotating frame T_1ρ(H) were measured via ¹³C CP/MAS NMR spectroscopy as a function of blend composition. In view of the T_1ρ(H) values, it is concluded that the PH and PES-C chains are intimately mixed on the scale of 20-30 Å. FTIR studies indicate that there were the intermolecular specific interactions in this blends, involved with the hydrogen-bonding between the hydroxyls of PH and the carbonyls of PES-C, and the strength of the intermolecular hydrogen bonding is weaker than that of PH self-association. At higher temperature, the PH/PES-C blends underwent phase separation. By means of thermal analysis, the phase boundaries of the blends were determined, and the system displayed the lower critical solution temperature behavior. Thermogravity analysis (TGA) showed that the blends exhibited the improved thermal stability, which increases with increasing PES-C content.     

Solid-state NMR studies on phase behavior and motional mobility in binary blends of polystyrene and poly(cyclohexyl methacrylate)

The phase behavior and motional mobility in binary blends of polystyrene (PS) and poly(cyclohexyl methacrylate) (PCHMA) have been investigated by solid state ¹³C NMR techniques. The blend miscibility has been studied by examining the ¹H spin-relaxation times in the laboratory frame (T₁^H) and in the rotating frame (T_1ρ^H) for the PCHMA/PS blends with various compositions and pure components. The T_1ρ^H results show that PCHMA and PS are intimately mixed at the molecular level within the blends at all compositions. In addition, according to the results of carbon T_1ρ relaxation time measurements, we conclude that mixing is intimate enough to cause a reduction in local chain mobility for PS, but an increase in side chain mobility for PCHMA.     

Synthesis and characterization of new vinyl acetate grafting onto epoxidized linseed oil in aqueous media

Modified poly (vinyl acetate) copolymers with epoxidized linseed oil (ELO) as co‐monomer have been prepared. The polymerization was performed in aqueous medium without any additional protective colloid in the presence of sodium persulfate as catalyst. The effect of vinyl acetate (VAc)/ELO feed ratio, reaction temperature, reaction time, and catalyst amount has been studied. FTIR spectroscopy showed that the reaction between ELO and VAc resulted in slight decrease and shift in ELO characteristic bands of oxirane groups; and new bands were detected in the copolymer spectra attributed to PVAc and ELO functional groups. Moreover, new signals attributable to the copolymer were observed in the ¹H NMR spectra (δ 4.07 and 1.62 ppm) and in the ¹³C NMR spectra (δ 15.29 and 31.0 ppm). Analysis by differential scanning calorimetry (DSC) showed a single T_g for the copolymerization product of VAc and ELO and two T_g for the PVAc/ELO blend, indicating the chemical reaction between VAc and ELO. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42089.     

Thermal and spectroscopic properties of zinc perchlorate/poly(vinylpyrrolidone) blends and a comparison with related hydrogen bonding systems

We have investigated the thermal and spectroscopic properties of blends of poly(vinylpyrrolidone) (PVP) with zinc perchlorate. Analyses by differential scanning calorimetry indicates that blending with zinc perchlorate increases the values of T_g of PVP. We calculated the interaction strength of the zinc salt/PVP blends based on an extended configuration entropy model. The presence of ion-dipole interactions between PVP and the zinc salt was confirmed based on Fourier transform infrared (FTIR) and solid-state NMR spectroscopies, which suggest that the zinc cations coordinate with the carbonyl groups of PVP. The single value of measured by solid-state NMR spectroscopy observed for all the zinc salt/PVP blends is smaller than that of pure PVP, which is a finding that indicates that the domain size of this blend system decreases upon increasing the zinc salt content. Based on FTIR and solid-state NMR spectroscopic analyses, we conclude that the ion-dipole interactions in the zinc salt/PVP blend are stronger than the hydrogen bonds in systems such as the poly(vinylphenol) (PVPh)/PVP blend and the PVPh-co-PVP copolymer.     

Preparation and characterization of novolac type phenolic resin blended with poly(dimethylsiloxane adipamide)

Phenolic resin/poly(dimethylsiloxane adipamide) (PDMSA) blends, which have been prepared, show miscibility due to intermolecular H‐bonding existing between phenolic resin and the PDMSA. The specific H‐bonding of novolac type phenolic/PDMSA blends was characterized by means of glass transition temperature behavior and Fourier Transform Infrared Spectroscopy (FTIR). The strength of intermolecular H‐bonding within the phenolic blend is a function of the H‐bonded group of the PDMSA modifier and corresponds to the deviation glass transition temperature (ΔT_g). Phenolic/PDMSA blends were completely miscible, as confirmed by the T_g study. The FTIR result is in good agreement with the inference from T_g behavior. The char yield of phenolic/PDMSA corresponds to the phenolic resin content. The molecular mobility of phenolic/PDMSA blends increases with PDMSA content in the phenolic‐rich region. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 984–992, 2002     

Self-Assembly structures through competitive interactions of miscible crystalline-amorphous diblock copolymer/homopolymer blends

A series of miscible crystalline-amorphous diblock copolymers, (poly(?-caprolactone)-b-(vinyl phenol), PCL-b-PVPh) were prepared through sequential ring-opening and controlled living free radical (nitroxide-mediated) polymerizations and then blended with poly(vinyl pyrrolidone) (PVP) homopolymer. Specific interactions, miscibility, and self-assembly morphologies mediated by hydrogen bonding interactions of this new A-B/C type blend, were investigated in detail. Micro-phase separation of these miscible PCL-b-PVPh diblock copolymers occurs by blending with PVP through competitive hydrogen bonding interaction in this A-B/C blend. FTIR, XRD, and DSC analyses provide positive evidences that the carbonyl group of PVP is a significantly stronger hydrogen bond acceptor than PCL, thus the PCL block is excluded from the PVPh/PVP miscible phase to form self-assembly structure. ¹³C CP/MAS solid-state NMR spectra provide additional evidence confirming that micro-phase separation occurs in the blend system because of the presence of more than two T_1ρ(H) values for this A-B/C blend system. According to the result of the FTIR and SAXS results, the smaller molecular weight system contains a greater fraction of the hydrogen-bonded carbonyl group, cause indirectly the high degree of phase separation among these blends. In addition, the SAXS profiles possess a sharp primary peak and highly long range ordered reflections q/q^∗ ratios of 1:2:3 at lower PVP content, an indication of the lamellar structure in the blend which is consistent with TEM image. The phase behavior and morphology shifts from lamellar to cylinder structure with further increase in the PVP content.     

Study of the nanomorphology of OC1C10-PPV/precursor-PPV blends by solid state NMR relaxometry

Films of conjugated polymer blends were studied by NMR relaxometry in order to improve the understanding of the nanomorphology and segmental chain mobility. Whereas optical microscopy was applied to obtain a rough impression about the surface morphology, the T_1H and T_2H NMR relaxation decay times were determined in the solid state (¹³C-CP/MAS and ¹H-wideline NMR) to judge the homogeneity of the phase morphology, to estimate the size of phase separated molecular domains and to compare the local segmental chain mobility. Besides blend composition, important parameters investigated are the film processing technique (dropcasting vs. spincoating), the casting solvent and the casting substrate.     

Miscibility and phase structure of binary blends of poly(L‐lactide) and poly(vinyl alcohol)

Blend films of poly(L ‐lactide) (PLLA) and poly(vinyl alcohol) (PVA) were obtained by evaporation of hexafluoroisopropanol solutions of both components. The component interaction, crystallization behavior, and miscibility of these blends were studied by solid‐state NMR and other conventional methods, such as Fourier transform infrared (FTIR) spectra, differential scanning calorimetry (DSC), and wide‐angle X‐ray diffraction (WAXD). The existence of two series of isolated and constant glass‐transition temperatures (T_g's) independent of the blend composition indicates that PLLA and PVA are immiscible in the amorphous region. However, the DSC data still demonstrates that some degree of compatibility related to blend composition exists in both PLLA/atactic‐PVA (a‐PVA) and PLLA/syndiotactic‐PVA (s‐PVA) blend systems. Furthermore, the formation of interpolymer hydrogen bonding in the amorphous region, which is regarded as the driving force leading to some degree of component compatibility in these immiscible systems, is confirmed by FTIR and further analyzed by ¹³C solid‐state NMR analyses, especially for the blends with low PLLA contents. Although the crystallization kinetics of one component (especially PVA) were affected by another component, WAXD measurement shows that these blends still possess two isolated crystalline PLLA and PVA phases other than the so‐called cocrystalline phase. ¹³C solid‐state NMR analysis excludes the interpolymer hydrogen bonding in the crystalline region. The mechanical properties (tensile strength and elongation at break) of blend films are consistent with the immiscible but somewhat compatible nature of these blends. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 762–772, 2001