Miscibility of poly(styrene-co-vinyl phenol) with poly(ɛ-caprolactone)

Summary Poly(styrene-co-vinyl phenol) (STVPh)/poly(-caprolactone)(PCL) blends showed enhanced miscibility over polystyrene/PCL blend, and showed single glass transition temperature when the contents of vinyl phenol (VPh) in copolymer were higher than 10 wt % (maximum content of VPh in STVPh used in this study was 20 wt%). STVPh 4, STVPh 7, STVPh 10 (4, 7, 10 were VPh wt%)/PCL blends showed cloud points on heating for miscible blend system, and this phase separation was reversible on cooling. From melting point depression of PCL, interaction parameter, B. for miscible STVPh 12/PCL blend system was evaluated.     

Compatibilisation of blends of poly(vinyl chloride) and poly(styrene-block-(ethylene-co-butadiene)-block–styrene) with maleic anhydride grafting

Abstract

The mechanical properties of blends of poly (vinyl chloride) (PVC) and poly (styrene-block-(ethylene-co-butadiene)-block–styrene) (SEBS) were investigated using maleic anhydride grafted SEBS (SEBS-g-MAH) as a compatibiliser. The results indicated that addition of a small amount of SEBS-g-MAH during melt blending significantly improved the mechanical properties of PVC/SEBS blends. The impact strength of the compatibilised PVC/SEBS blends was found to reach a maximum of 53·5±2·78 KJ m^?2 at room temperature and a maximum of 32·8±1·66 KJ m^?2 at ?20°C at an SEBS-g-MAH loading level of 6 phr. The two glass transition temperatures of the components in the blends converged to some degree upon addition of SEBS-g-MAH for compatibilisation. At room temperature the dynamic storage modulus of the compatibilised blends was higher than that of the blends without compatibilisation. The size of the dispersed phase domains in the blends was appreciably reduced on addition of SEBS-g-MAH during melt blending according to scanning electron microscopy. All the above observations revealed that SEBS-g-MAH enhanced the compatibility between PVC and SEBS in the PVC/SEBS blends.     

In vitro degradation of poly(l-lactide)/poly(ε-caprolactone) blend reinforced with MWCNTs

The physical and mechanical properties of poly(l-lactide)/poly(??-caprolactone) (PLLA/PCL) blends reinforced with multiwalled carbon nanotubes (MWCNTs) before and after in vitro degradation were investigated. Because of brittleness, PLLA needs to be plasticized by PCL as a soft polymer. The MWCNTs are used to balance the stiffness and the flexibility of PLLA/PCL blends. The results showed that with incremental increase in concentration of MWCNTs in composites, the agglomerate points of MWCNTs were increased. The physical and mechanical properties of prepared PLLA/PCL blends and MWCNT/PLLA/PCL nanocomposites were characterized. The X-ray diffraction analysis of the prepared blends and composites showed that MWCNTs, as heterogeneous nucleation points, increased the lamella size and therefore the crystallinity of PLLA/PCL. The mechanical strength of blends was decreased with incremental increase in PCL weight ratio. The mechanical behavior of composites showed large strain after yielding and high elastic strain characteristics. The tensile tests results showed that the tensile modulus and tensile strength are significantly increased with increasing the concentration of MWCNTs in composites, while, the elongation-at-break was decreased. The in vitro degradation rate of polymer blends in phosphate buffer solution (PBS) increased with higher weight ratio of PCL in the blend. The in vitro degradation rate of nanocomposites in PBS increased about 65% when the concentration of MWCNTs increased up to 3% (by weight). The results showed that the degradation kinetics of nanocomposites for scaffolds can be engineered by varying the contents of MWCNTs.     

Miscibility behaviour of sulfonylated poly(2,6-dimethyl-1,4-phenylene oxide) copolymers in the blends with poly(styrene-co-maleic anhydride) and with poly(α-methylstyrene-co-maleic anhydride)

Summary The miscibility behaviour of sulfonylated poly(2,6-dimethyl-1,4-phenylene oxide) of the different degree of sulfonylation blended with poly(styrene-co-maleic anhydride) or poly(-methylstyrene-co-maleic anhydride) was studied. The critical degree of sulfonylation for phase separation in these blends was found to be 55 mole % and 66 mole %, respectively. The miscibility behaviour was analyzed on the basis of the mean field treatment and studied by DSC.Dedicated to Professor Dragutin Fle in honor of his 70th birthday     

Thermal properties of di- and triblock copolymers of poly(l-lactide) with poly(oxyethylene) or poly(ε-caprolactone)

High molecular weight di- and triblock copolymers of poly(l-lactide), PLLA, (80 wt%) with a crystallizable flexible second component such as poly(ε-caprolactone), PCL, or poly(oxyethylene), PEO, (20 wt%) were obtained in nearly quantitative yields by ring opening of l-lactide initiated by PCL or PEO hydroxy terminated macromers. The copolymers were characterized by ¹H NMR and FTIR spectroscopy and size exclusion chromatography and showed unimodal and narrow molecular weight distributions. X-ray diffraction measurements revealed high crystallinity (38-56%) of the PLLA blocks and gave no clear evidences of PCL or PEO crystallinity. DMTA and DSC techniques showed a melting behaviour of the copolymers (T_m=174-175 °C; ΔH_m=19-37 J/g) quite similar to that of PLLA. PCL and PLLA segments are immiscible, while PLLA and PEO segments are partially miscible in the amorphous phase. Stress-strain measurements indicated a ductile behaviour of the copolymers, characterized by lower tensile moduli (225-961 Pa) and higher elongations at break (25-134%) with respect to PLLA.     

Rheological properties of poly(ε-caprolactone) and poly(styrene-co-acrylonitrile) blends

Summary Rheological properties of poly(-caprolactone) (PCL) and Poly (styrene-co-acrylonitrile) (SAN) blends were examined as a function of the acrylonitrile (AN) content in SAN, to systematically understand the correlation between the interaction parameter and the theological properties of miscible polymer blends. When the plateau modulus (G _N ⁰) and zero shear viscosity ( ₀) of the PCL/SAN blends are plotted against the AN content in SAN, a minimum is observed. Qualitatively, the results obtained parallel the variation of the interchain interaction with the AN content. The negative deviation ofG _N ⁰ and ₀ from linearity seems to be attributed to the increase in the entanglement molecular weight between dissimilar chains which results from the chain extension caused by interchain interaction.     

Synthesis and characterization of polyrotaxanes comprising α-cyclodextrins and poly(ε-caprolactone) end-capped with poly(N-isopropylacrylamide)s

Biodegradable polyrotaxane (PR)-based triblock copolymers were synthesized via the atom transfer radical polymerization (ATRP) of N-isopropylacrylamide (NIPAAm) initiated with polypseudorotaxanes (PPRs) consisting of a distal 2-bromopropiomyl bromide end-capping poly(ε-caprolactone) (Br-PCL-Br) and a varying amount of α-cyclodextrins (α-CDs) in the presence of Cu(I)Br/PMDETA at 25 °C in aqueous solution. The copolymers were featured by relatively higher yields from 46.0% to 82.8% as compared with previous reports. Their structure was characterized in detail by using ¹H NMR, ¹³C CP/MAS NMR, GPC, WXRD, DSC and TGA analyses. When a feed molar ratio of NIPAAm to Br-PCL-Br was changed from 50 to 200, the degree of polymerization of PNIPAAm blocks attached to two ends of PPRs was in a range of 158–500. About one third of the added α-CDs were still entrapped on the central PCL chain after the ATRP process. Attaching PNIPAAm rendered the copolymers soluble in aqueous solution showing the thermo-responsibility as evidenced by turbidity measurements.     

Effects of liquid–liquid phase separation on crystallization of poly(ethylene glycol) in blends with isotactic poly(methyl methacrylate)

To analyze the interplay between crystallization and liquid–liquid phase separation (LLPS), isothermal crystallization behavior of poly(ethylene glycol) (PEG) in blends with isotactic poly(methyl methacrylate) (i-PMMA) was investigated by differential scanning calorimetry (DSC). The blend system had an upper critical solution temperature (UCST) type phase diagram. When the crystallization occurred simultaneously with LLPS, the overall crystallization rate was enhanced at high crystallization temperatures T_c, relatively compared with that of neat PEG. This behavior was interpreted by the combination of the effects of spinodal quench depth ?T_s and usual supercooling degree ?T_c, according to the theory of Mitra and Muthukumar, namely, the crystallization rate is enhanced by the concentration fluctuation-assisted nucleation at high T_c. In the crystallization after LLPS proceeded, on the other hand, the overall crystallization rate was slow and less dependent on the blend composition. In addition, it was revealed by small-angle X-ray scattering measurements that amorphous i-PMMA was excluded from the interlamellar region of PEG crystals in SQ as well as WQ.     

Mechanism of thermal generation of poly(p-phenylene vinylene) from poly(p-xylene-α-dimethylsulphonium halides)

The thermal conversion of poly(p-xylene-α-dimethylsulphonium halides) into poly(p-phenylene vinylene) (PPV) can occur through two concomitant reactions. The principal reaction is an elimination of dimethyl sulphide and halogen acid, while the second reaction, an undesirable one, is the nucleophilic attack of the halide counterion on a methyl group to form the methyl halide and a methyl sulphide. The two thermal processes were observed in the pyrolysis of both poly(p-xylene-α-dimethylsulphonium bromide) and poly(p-xylene-α-dimethylsulphonium chloride). On storage at room temperature, poly(p-xylene-α-dimethylsulphonium halides) undergo partial decomposition to PPV, as shown by thermogravimetric experiments. The flash pyrolysis-gas chromatography-mass spectrometry of PPV obtained by the thermal conversion of poly(p-xylene-α-dimethylsulphonium bromide) at 400°C was also investigated.     

Mechanical properties of transparent poly(methyl methacrylate) nanocomposites reinforced with core–shell polyacrylonitrile/poly(methyl methacrylate) nanofibers

Having considered the mechanical and optical properties related to microstructure, the authors of the present work did a study of the in situ interface formation between polyacrylonitrile/poly(methyl methacrylate) (PAN/PMMA) core–shell nanofibers and PMMA resin so as to prepare reinforced PMMA nanocomposites (NCs). The NCs were produced using the dip-coating method. The core–shell nanofibers were generated via phase separation of PAN/PMMA solution during the conventional electrospinning. The results of attenuated total reflection-Fourier transform infrared spectroscopy, transmission electron microscope, and energy dispersive X-ray spectrometer confirmed the formation of core–shell structure of the PAN/PMMA nanofibers. According to the findings of the study, the NCs reinforced with 1.7% volume fractions (v _f) of the core–shell nanofibers, having the composition of 50/50 (PAN/PMMA), had the highest tensile and bending properties. The obtained results showed that by increasing the v _f of nanofibers from 1.7 to 2.9%, the tensile and bending moduli increased by 29.9 and 44.2%, respectively. Increasing v _f to 5.7% decreased the just-mentioned properties. Moreover, the transparency of NCs decreased by less than 1, 10, and 18%, respectively, when the aforementioned volume fractions were applied. The theoretical values for the tensile modulus were calculated using the models proposed by Manera, Pan, and Halpin–Tsai–Nielsen. The best prediction was made when the model proposed by Halpin–Tsai–Nielsen was applied.     

Crystallization and morphology of poly(ethylene succinate) and poly(β-hydroxybutyrate) blends

Summary The melting and crystallization behavior of poly(β-hydroxybutyrate) (PHB) and poly(ethylene succinate) blends has been studied by differential scanning calorimetry and optical microscopy. The results indicate that PHB and PES are miscible in the melt. Consequently the blend exhibits a depression of the melting temperature of both PHB and PES. In addition, a depression of the equilibrium melting temperature of PHB is observed. The Flory-Huggins interaction parameter (χ₁₂ ), obtained from melting point depression data, is composition dependent, and its value is always negative. Isothermal crystallization in the miscible blend system PES/PHB is examined by polarized optical microscope. The presence of the PES component gives a wide variety of morphologies. The spherulites exhibit a banded structure and the band spacing decreases with increase PES content. Received: 29 June 1998/Revised version: 31 August 1998/Accepted: 10 September 1998     

DSC studies of poly(vinyl chloride)/poly(ε-caprolactone)/poly(ε-caprolactone)-b-poly(dimethylsiloxane) blends

Poly(vinyl chloride)/poly(ε-caprolactone)/poly(ε-caprolactone)-b-poly(dimethylsiloxane) [PVC/PCL/(PCL-b-PDMS)] blends were prepared by solvent casting from tetrahydrofuran. The content of PVC was kept constant (60 wt%); the PCL and PCL-b-PDMS contents were varied by replacing different amounts of PCL [0–20 wt% from the PVC/PCL (60/40) blend] with PCL-b-PDMS copolymer having different molecular weights of the PCL blocks. The thermal properties of prepared blends were investigated by differential scanning calorimetry in order to analyse miscibility (through glass transition temperature) and crystallinity. Differential scanning calorimetry analyses show that the PVC/PCL/PCL-b-PDMS blends are multi-phase materials which contain a PVC plasticized with PCL phase, a block copolymer PCL-b-PDMS phase (with crystalline and amorphous PCL and PDMS domains) and a PCL phase (preponderantly crystalline).     

Crystallization behavior of poly(β-propiolactone)-block-polyethylene copolymers with varying polyethylene crystallinities

The crystallization behavior of poly(β-propiolactone)-block-polyethylene (PPL-b-PE) copolymers with high PE crystallinities χ_PE (>0.30) has been examined using time-resolved synchrotron small-angle X-ray scattering and Fourier transform infrared spectroscopy, where the PE block crystallized first and subsequently the PPL block crystallized on quenching from a strongly segregated melt. The crystallization of PE blocks destroyed the lamellar microdomain structure (LMS) existing in the melt to form the crystalline lamellar morphology (CLM), and then PPL blocks crystallized within CLM. This morphology formation was compared to our previous results for the crystallization of PPL-b-PE copolymers with low χ_PE (0.12 < χ_PE < 0.26), where the crystallizability of PE blocks was not sufficiently large to destroy LMS. As a result, PE blocks crystallized promptly within LMS to reinforce and stabilize it against the subsequent crystallization of PPL blocks, yielding the confined crystallization of both blocks within LMS. We summarize these results including the case of χ_PE = 0, and propose three mechanisms of morphology formation occurring in PPL-b-PE copolymers according to χ_PE (i.e., high, low, or zero).     

One-step synthesis of pH-sensitive poly(Acrylamide-co-Sodium Acrylate) beads with core–shell structure

This work describes a novel one-step method to prepare poly(AMm-co-AAcNa) pH-sensitive hydrogel beads with core–shell structure induced by a spontaneous phase separation process during polymerization. In virtue of the phase separation process, polymers with high molecular weight separate to the core phase whereas monomers are left in the shell. This redistribution inside the droplets enables the polymerization environment change sharply to endow the beads with different network structure in core and shell. FTIR spectrum and EDS show that core and shell share identical composition; yet GPC exhibits a bimodal molecular weight distribution which lead to a conventional network in core but a rich-in-branch network in shell. This difference in structure results in mainly three discrepancies in performance. The level of volume change that the beads exhibit at about pH = 4 is much more intense for shell than for core; the swelling/shrinking kinetics of the core and shell indicates that shell responses about 30 times faster than core does; fitting of the absorbency capacity exhibited that the ones of the core and shell are about 67 g/g and 2126 g/g, respectively. A microfluidic device with co-axial channel structure is introduced in this fabrication. The hydrogel beads exhibited narrow size distribution and the diameter of core and shell could be freely controlled by the high controllability of microfluidic technology and by manipulating the phase separation process. In sum, this method impart us an easy and fast-running way to obtain hydrogel beads with core–shell structure, which has potential in various applications like optical material, lenses and sensors.     

Thermal decomposition of some poly(β-hydroxyalkanoates)

The thermal decomposition of some polyhydroxyalkanoates (PHA) has been investigated by means of thermogravimetry and differential thermogravimetry. The thermal stability of the studied polyesters decreases slightly with increasing hydroxyvalerate (HV) comonomer. This result is different from those reported in the literature. Other results agree with reaction mechanisms proposed in the literature. The data from dynamic thermogravimetric experiments are consistent with a first order reaction, as would be expected from the reaction mechanism. Infrared spectra of the thermally degraded and undegraded copolymers are evidence of the cis-elimination mechanism. © 1999 Society of Chemical Industry     

Miscibility of poly(α-methyl styrene-co-methacrylic acid) with alkyl methacrylate-co-4-vinylpyridine copolymers

Summary The miscibility of blends of poly(-methyl styrene-co-methacrylic acid) (PMSMA) with various alkyl methacrylate polymers or poly(alkyl methacrylate-co-4-vinylpyridine) was studied by differential scanning calorimetry and Fourier transform infra red spectroscopy. PMSMA is immiscible with poly(methyl methacrylate), poly(ethyl methacrylate) and poly(n-butyl methacrylate). The introduction of 4-vinylpyridine by random free radical copolymerization within these alkyl methacrylate polymer chains enhanced the miscibility of these copolymers with PMSMA as a result of specific interactions that occurred between the carboxylic and pyridine groups, evidenced from the significant changes observed by FTIR in the carboxyl and pyridine ring regions. The density of interacting groups required for miscible blends depends on the size of the pendant group.     

Effect of poly(ε-caprolactone) and titanium (IV) dioxide content on the UV and hydrolytic degradation of poly(lactic acid)/poly(ε-caprolactone) blends

The effect of accelerated weathering degradation on the properties of poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blends and PLA/PCL/titanium (IV) dioxide (TiO₂) nanocomposites are presented in this paper. The results show that both polymers are susceptible to weathering degradation, but their degradation rates are different and are also influenced by the presence of TiO₂ in the samples. Visual, microscopic and atomic force microsocpy observations of the surface after accelerated weathering tests confirmed that degradation occurred faster in the PLA/PCL blends than in the PLA/PCL/TiO₂ nanocomposites. The X-ray diffraction results showed the degradation of PCL in the disappearance of its characteristic peaks over weathering time, and also confirmed that PLA lost its amorphous character and developed crystals from the shorter chains formed as a result of degradative chain scission. It was further observed that the presence of TiO₂ retarded the degradation of both PLA and PCL. These results were supported by the differential scanning calorimetry results. The thermogravimetric analysis results confirmed that that PLA and PCL respectively influenced each other's thermal degradation, and that TiO₂ played a role in the thermal degradation of both PLA and PCL. The tensile properties of both PLA/PCL and PLA/PCL/TiO₂ were significantly reduced through weathering exposure and the incorporation of TiO₂.     

High-pressure solution blending of poly(?-caprolactone) with poly(methyl methacrylate) in acetone + carbon dioxide

The miscibility of blends of poly(?-caprolactone) (PCL, M_w = 14,300) with poly(methyl methacrylate) (PMMA, M_w = 15K or 540K) in acetone + CO₂ mixed solvent has been explored. The liquid-liquid phase boundaries at different temperatures have been determined for mixtures containing 10 wt% total polymer blend, 50 wt% acetone and 40 wt% CO₂. The PCL and PMMA contents of the blends were varied while holding the total polymer concentration at 10 wt%. The polymer blend solutions all displayed LCST-type behavior and required higher pressures than individual polymer components for complete miscibility. Complete miscibilities were achieved at pressures within 40 MPa. The DSC scans show that the blends are microphase-separated. The blends display the melting transition of PCL and the glass transition temperature of the PMMA phases. The presence of PMMA is found to influence the crystallization and melting behavior of PCL in the blends. The DSC results on heat of melting and the FTIR spectra, specifically the changes at 1295 cm⁻¹ band show the changes (decrease) in overall crystallinity of the blend upon addition of PMMA.     

The crystallization behavior of poly(ethylene glycol)-poly(ε-caprolactone) diblock copolymers with asymmetric block compositions

Crystallization behavior, structural development and morphology evolution of a series of poly (ethylene glycol)-poly(ε-caprolactone) diblock copolymers (PEG-b-PCL) were investigated via differential scanning calorimetry (DSC), X-ray diffraction (XRD) and atomic force microscopy (AFM). In these copolymers, both blocks were crystallizable and biocompatible. The mutual effects between the PEG and PCL blocks were significant, leading to the obvious block composition dependence of the crystallization behavior and morphology of the PEG-b-PCL copolymers. The relative block length determined which block crystallized first. The temperature-dependent XRD measurements confirmed which block crystallized first from the copolymer during the cooling procedure. Single crystals of the PCL and PEG homopolymers and the PEG-b-PCL copolymers were obtained and observed by AFM. The block (PCL or PEG) crystallized first would determine the crystal morphology. The block crystallized later acted as a solvent, which was advantageous to forming perfect single crystals of the whole block copolymers.     

Modeling of interdiffusion in poly(vinyl acetate)–poly(methyl methacrylate)–toluene multicomponent systems

Work on interdiffusion has been mainly carried out in binary systems in the past, and this work has focused on polymer–solvent (S) systems and polymer blends. To understand and predict the interdiffusion of two solids in the presence of one S, we present a new mathematical model based on the Onsager approach. Within our model, interdiffusion kinetics are described with a modification of the reptation model for long polymer chains, and the chemical potential gradient is used as the driving force behind mass transfer. The chemical potential is calculated with a Flory–Huggins approach. The model was validated with 29 Raman spectroscopy experiments in poly(vinyl acetate)–poly(methyl methacrylate)–toluene systems at 20 °C. Monomer mobilities (L _i,0s) were determined for both polymers to show the independence of L _i,0 from the chain length. The L _i,0s were found to be strongly dependent on the S content. With the knowledge of phase equilibria and L _i,0s, interdiffusion in the ternary polymer–polymer–S system could be predicted by the introduced model. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47092.