Segmental orientation in blends of poly(ϵ-caprolactone) with poly(vinyl chloride) and nitrocellulose

Binary blends of polycaprolactone (PCL) with poly(vinyl chloride) (PVC) and nitrocellulose (NC) have been shown to be compatible over a wide range of composition. In this study, segmental orientation was determined by dynamic, differential infrared dichroism for each component in the PVC and NC blends with PCL. In compatible amorphous blends, PCL orientation behavior was essentially the same as for the orientation of NC or the isotactic segments of PVC. Syndiotactic PVC segments showed higher orientations, reflecting the greater intrachain stiffness of the microcrystalline PVC phase. PCL segments in the blends where the PCL component was semicrystalline were found to exhibit orientation characteristics which were quite different from the orientation of the nitrocellulose and PVC components of the blends. By assuming that the NC orientation represented the response of the amorphous PCL, the orientation of the crystalline PCL was determined for a NC blend using a simple model of additive dichroism response. In PVC blends, a similar analysis using the amorphous-component response of PVC was made. In both cases the results from the dichroism model showed fair agreement with the PCL unit cell C-axis orientation from independent dichroism calculations.     

An investigation of the compatibility and morphology of semicrystalline poly(ε-caprolactone)–poly(vinyl chloride) blends

Blends of poly(ε-caprolactone) (PCL) and poly(vinyl chloride) (PVC) were investigated at concentrations of PCL greater than 50 wt % using purified materials. For these concentrations, PCL partially crystallizes with degrees of crystallinity ranging from 50% for pure PCL to < 10% for the 50% mixture. Small-angle x-ray scattering was used to characterize the resultant morphologies. Model calculations for the interference functions and for the integrated scattering indicate that PVC is incorporated between the PCL lamellae and that the two polymers form a homogeneous mixture in the amorphous phase. These results were compared to previous results on the same system using the identical technique. Purification of the two homopolymers proved to play a critical role in the overall mixing characteristics of PVC and PCL     

Fourier-transform infrared studies of polymer blends. II. Poly(ϵ-caprolactone)–poly(vinyl chloride) system

Fourier-transform infrared (FTIR) studies of the poly(?-caprolactone) (PCL)–poly(vinyl chloride) (PVC) blend system are presented. The results indicate that there are specific interactions between the PCL and PVC in both the molten and solid states which could be responsible for the apparent compatibility of the amorphous component of these blends. Additionally, FTIR difference spectra are presented to illustrate the potential of this technique for following the kinetics of crystallinity in polymer blend systems.     

The microstructure of poly(vinyl chloride) as revealed by x-ray and light scattering

Small-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS) as well as small-angle light-scattering (SALS) techniques have been applied to investigate the microstructure of a number of commercial poly(vinyl chloride) (PVC) samples. From the wide-angle x-ray scattering, crystallinity and crystal size parameters have been determined. The crystallinity of the samples investigated range from 5% to 10%. Superstructure parameters such as crystallite thickness, distribution functions of crystallite and amorphous thicknesses, and size of ordered regions have been obtained by an analysis of the SAXS curves using the cluster model. The crystallinity agrees well with the WAXS crystallinities indicating that most of the crystals are lamellar shaped, though some rodlike entities are present in the sample as is shown by the small-angle light scattering. From the SAXS analysis, the microstructure is described as clusters of lamella stacks which are identical with the subprimary particles. Their size is determined to be 220–240 Å. Emulsion type PVC also contains lamellar-shaped crystals. The superstructure, however, of this type of PVC is different from that of mass or suspension-polymerized material. The SAXS curve does not reveal any correlation between the crystals.     

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

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

Intramolecular interactions in poly(styrene-co-acrylonitrile)/poly(ε-caprolactone) blends

Specific interactions in blends of poly(ε-caprolactone) (PCL) and poly(styrene-co-acry-lonitrile) (SAN) were studied as a function of copolymer composition and blend ratio by using Fourier-transform infrared spectroscopy (FTIR). It was shown that miscibility occurred within a certain range of copolymer compositions because the presence of PCL reduced the thermodynamically unfavorable repulsion between styrene and acrylonitrile segments in the random copolymer. This effect was observed in terms of a shift to higher frequencies in the 700 cm^-1 γ-CH out-of-plane deformation vibration absorption of styrene and in the approximately 2236 cm^?1 C?N stretching frequency band in acrylonitrile segments. Specific intermolecular interactions between SAN and PCL were not observed in this study. © 1993 John Wiley & Sons, Inc.     

PDMS migration at poly(vinyl chloride)/poly(ɛ-caprolactone)/poly(ɛ-caprolactone)-b-poly(dimethylsiloxane) blends surfaces

Films composed of poly(vinyl chloride)/poly(?-caprolactone)/poly(?-caprolactone)-b-poly(dimethylsiloxane) [PVC/PCL/(PCL-b-PDMS)] blends were prepared by solvent casting from tetrahydrofuran. The PVC content was kept constant (60 wt %) while varying the PCL and PCL-b-PDMS contents, part of the PCL (0–20 wt %) in the PVC/PCL (60/40) blend being replaced with PCL-b-PDMS with different molecular weights of the PCL blocks. The prepared blends were investigated by infrared spectroscopy and contact angle measurements. FTIR analysis and contact angle measurements indicate that the PDMS blocks tend to migrate towards the surface and this migration is preferential to the side in contact with air.     

Miscibility of poly(ϵ-caprolactone) and of poly(styrene-co-acrylonitrile) with poly(styrene-co-acrylic acid)

The miscibility of poly (?-caprolactone) (PCL) with poly (styrene-co-acrylic acid) (SAA) and of poly (styrene-co-acrylonitrile) (SAN) with SAA was examined as a function of the comonomer composition in the copolymers. For PCL/SAA blends it was found that PCL is miscible with SAA within a specific range of copolymer compositions. Segmental interaction energy densities were evaluated by analysis of the equilibrium melting point depression and application of a binary interaction model. The results suggest that the intramolecular repulsion in SAA copolymer plays an important role in inducing the miscibility. Additionally, the critical AA content in SAA for the blend to be homogeneous was predicted by correlating the segmental interaction energy densities with the binary interaction model. For SAN/SAA blends, it was also found that SAA is miscible with SAN within a specific range of copolymer compositions. From the binary interaction model, segmental interaction energy denisties between different monomer units were estimated from the miscibility map and were found to be positive for all pairs, indicating that the miscibility of the blends is due to the strong repulsion in the SAA copolymers.     

Binary and ternary poly(lactic acid)/poly(ϵ-caprolactone) blends: The effects of oligo-ϵ-caprolactones upon mechanical properties

Oligo-ε-caprolactones(o-CL) have been utilized as principle secondary components within poly(lactic acid)[PLA]-based blends as well as additives within larger-sized PCL/PLA blends in an effort to fully complement the mechanical attributes of the respective polyesters. Dynamic mechanical thermal analysis(DMTA) shows that the presence of o-CL plasticizes the PLA non-crystalline phase with a more pronounced effect seen as the size of o-CL is reduced. Moreover, it appears that the size of o-CL could also affect the static mechanical properties of the ternary systems as material stiffness and strength reside between those properties measured for high molecular weight PCL/PLA binary blends and the PLA homopolyester. Future work will examine the ability of these blends to sustain these properties during hydrolytic exposure.     

Dielectric,ultrasonic and x-ray diffraction studies on poly(vinyl chloride)-chlororubber-20 blends

Poly(vinyl chloride)-chlororubber-20 blends have been studied for compatibility by dielectric, ultrasonic and X-ray diffraction techniques. It has been found by both ultrasonic and dielectric techniques that poly(vinyl chloride) forms compatible blends with chlororubber-20 over a wide range of composition. X-ray diffraction studies indicate polymer-polymer interaction and reduction in the crystallinity of poly(vinyl chloride) by the incorporation of chlororubber-20. These results agree with earlier observations and have been explained in terms of the molecular and morphological behaviour of the blends.     

Small-angle x-ray and neutron scattering studies of amorphous polymer blends

Dilute mixtures of poly(ε-caprolactone) (PCL) in poly(vinyl chloride) (PVC), poly(p-iodostyrene) (PpIS) in polystyrene, and deuterated polystyrene (d-PS) in protonated poly(o-chlorostyrene) (PoCIS) were investigated by means of small-angle x-ray scattering and small-angle neutron scattering. The radii of gyration of PCL in PVC and of d-PS in PoCIS were found to be expanded over the θ values by 50 and 30%, respectively. Values of the second virial coefficient were positive although errors prevented definitive evaluation of the interaction parameter. PpIS was found to aggregate, with both the radius of gyration and molecular weight increasing with concentration. Concentrated mixtures of PCL and PVC were also investigated by using the Debye–Bueche correlation function analysis. Correlation distances indicated good mixing throughout the entire composition range.     

Brillouin light scattering from poly(vinyl chloride) gels

The hypersonic velocity and attenuation in PVC gels have been measured as a function of gel network volume fraction, using the technique of Brillouin light scattering. The experimental data have been analysed using the full theory for the elastodynamics of gels proposed recently by Johnson. It has been found that for two asymptotic approximations of the dynamic damping factor the tortuosity parameter is nearly always less than unity, contrary to the theoretical expectation.     

Morphology and properties of poly(vinyl chloride)–poly(butadiene-co-acrylonitrile) blends

The objective of this research was to study the structure-property relationships of two poly(vinyl chloride) (PVC)–poly(butadiene-co-acrylonitrile) (BAN) blends which exhibit differences in blend compatibility. Studies were carried out utilizing differential scanning calorimetry, dynamic mechanical testing, stress–strain, transmission electron microscopy (TEM), and infrared dichroism experiments at different temperatures. The BAN 31/PVC (BAN containing 31% acrylonitrile) system is considered to be nearly compatible as evidenced by T_g shifts, stress–strain results, orientation characteristics, and TEM micrographs. Similar experiments indicate that the BAN 44/PVC system is incompatible, and contains a mixed phase of BAN 44-PVC and a pure BAN 44 phase. The extent of heterogeneity in the compatible BAN 31/PVC system, however, plays an important role in the orientation characteristics of the blends.     

Interplay of fractionated crystallization and morphology in polypropylene/poly(ϵ‐caprolactone) blends

The thermal behavior of melt‐mixed polypropylene (PP)/poly(?‐caprolactone) (PCL) blends was investigated with differential scanning calorimetry, and it was quantitatively related to the morphology observed through scanning electron microscopy. The PP/PCL blends were immiscible in the whole composition range; however, some interesting phenomena were found. Blends with low PP contents crystallized in a fractionated fashion. By applying a self‐nucleation procedure, we demonstrated that this occurred because of a lack of highly active heterogeneities within the confined PP domains. On the other hand, PP acted as a nucleating agent for PCL, and when the PP content was reduced, the higher surface/volume ratio increased its nucleating activity. The nucleating effect was improved when the PP was self‐nucleated because of the better nucleating effect of PP annealed crystals. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1365–1379, 2007     

Periodic radial growth in ring-banded spherulites of poly(ε-caprolactone)/poly(styrene-co-acrylonitrile) blends

The isothermal crystallization process of a PCL/SAN blend (90/10 wt.-%) was investigated by using real time image analysis and hot stage optical microscopy. It was found that the growth rate of ringbanded spherulites in the isothermal crystallization process is not constant. Slow growth occurs in the bright bands, while fast growth is found in the dark bands. The radially unequal growth rate of ring-banded spherulites in PCL/SAN blends may be related to the convex band structure on the surface. This new discovery gives us the idea that rhythmic growth is effective in the growth process of ring-banded spherulites.     

Thermal degradation studies in poly(vinyl chloride)/poly(methyl methacrylate) blends

The miscibility, morphology, and thermal properties of poly(vinyl chloride) (PVC) blends with different concentrations of poly(methyl methacylate) (PMMA) have been studied. The interaction between the phases was studied by FTIR and by measuring the glass transition temperature (T_g) of the blends using differential scanning calorimetry. Distribution of the phases at different compositions was studied through scanning electron microscopy. The FTIR and SEM results show little interaction and gross phase separation. The thermogravimetric studies on these blends were carried out under inert atmosphere from ambient to 800 °C at different heating rates varying from 2.5 to 20 °C/min. The thermal decomposition temperatures of the first and second stage of degradation in PVC in the presence of PMMA were higher than the pure. The stabilization effect on PVC was found most significant with 10 wt% PMMA content in the PVC matrix. These results agree with the isothermal degradation studies using dehydrochlorination and UV-vis spectroscopic results carried out on these blends. Using multiple heating rate kinetics the activation energies of the degradation process in PVC and its blends have been reported.     

Synthesis and characterization of poly(ϵ-caprolactone)-poly(ethylene glycol) block copolymer

Poly(ϵ-caprolactone)–poly(ethylene glycol)–poly(ϵ-caprolactone) triblock copolymers (PECL) covering a wide range of poly(ethylene glycol) (PEG) lengths were synthesized with alkali metal alkoxide derivatives of poly(ethylene glycol). The effects of various factors, such as amount of the initiator, reaction time and temperature, polarity of solvent, length of PEG segment, and counterion on the polymerization were investigated. The copolymers were characterized by ¹H-NMR, IR, GPC, and DSC. It was found that THF system is superior to toluene system. The conversion of the monomer increased with increase of the initiator concentration. High molecular weight of the copolymer and high conversion of the monomer was obtained at below 30°C within 5 min. The polymerization process was studied by GPC and the coexistence of propagation and transesterification reaction was found, which leaded to relatively broad molecular weight distribution of the copolymers. © 1997 John Wiley & Sons, Inc.     

Influence of hyperbranched against linear architecture on crystallization behavior of poly(ε‐caprolactone)s in binary blends with poly(vinyl chloride)

Nonisothermal and isothermal crystallization behaviors of the hyperbranched poly(ε‐caprolactone) (HPCL)/poly(vinyl chloride) (PVC) and linear poly(ε‐caprolactone) (LPCL)/(PVC) blends were characterized with various blend composition such as 100/0, 95/5, 90/10, and 80/20, respectively. HPCL was synthesized through polycondensation of AB₂ macromonomer while LPCL and PVC were commercially purchased. The architectural characterization performed on ¹H NMR spectra revealed that HPCL consisted of about 3 AB₂ units and the linear segments consisted of 25 ε‐CL units. Through the nonisothermal crystallization analyses by modified Avrami approach with DSC crystallization exotherms, it was found that the crystallization rate was retarded by the increase in the noncrystallizable component (PVC) in the blends. This is in good agreement with the results of the isothermal crystallization analyses where time resolved small angle light scattering (SALS) and polarized optical microscopy (POM) were used. The effect of molecular architectural difference between HPCL and LPCL on the crystallization of their binary blends with PVC was elucidated by comparing the crystallization kinetic parameters. Both the nonisothermal and isothermal crystallization analyses showed that the crystallization rates of HPCL/PVC blends was faster than LPCL/PVC blends at given blend compositions. The faster crystallization of the HPCL/PVC blends is ascribed to the two specific architectural characteristics of HPCL; the branched structure and the incorporated long linear segments. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 577–589, 2007     

Complex formation of poly(ε-caprolactone) with cyclodextrin

Poly(ε-caprolactone) was found to form inclusion complexes with α-cyclodextrin to give crystalline compounds. The complexes are stoichiometric one-to-one (cyclodextrin: monomer unit) compounds. The yields of the complexes decreased with increasing the molecular weight of the polymer. They were characterized by IR, ¹H NMR, ¹³C CP/MAS NMR, and X-ray diffraction. The inclusion modes are discussed.