Miscibility of polyester/nitrocellulose blends: A DSC and FTIR study

The miscibility of polyester/nitrocellulose blends was investigated by differential scanning calorimetry and Fourier-transform infrared (FTIR) spectroscopy. Two nitrocelluloses (NC) derived from wood and having different nitrogen contents (12.62 and 13.42%) were used. On the basis of the glass transition temperature criterion, poly(?-caprolactone) (PCL), poly(valerolactone), poly(ethylene adipate), and poly(butylene adipate) are miscible with nitrocellulose, whereas poly(α-methyl α-propyl β-propiolactone) and poly(α-methyl β-proiolactone) are immiscible. The T_g versus composition curves of PCL/NC blends do not follow a monotone function but exhibit a singular point at a critical PCL volume fraction of 0.51 for NC-1342 and 0.45 for NC-1262 in agreement with Kovacs' theory. A shift of 17 cm^-1 of the carbonyl stretching band was observed with PCL/NC blends and is taken as evidence for hydrogen bonding interaction between the PCL carbonyl group and NC hydroxyl group. The frequency difference between the free hydroxyl absorbance and the absorbances of the hydrogen-bonded species was found to be 85 cm^-1 in pure NC and 125 cm^-1 in PCL/NC blends; it indicates that the average strength of this interaction is stronger than the corresponding self-associated hydrogen bonding in pure NC. The presence of a dipole-dipole interaction between the nitrate-ester groups of NC and the carbonyl groups of the polyesters is reported. The relative strength of the hydrogen bonding and dipole-dipole interactions is discussed and correlated with polymer miscibility.     

Miscible blends prepared from two crystalline polymers

Differential scanning calorimetry was used to determine the miscibility behavior of several polyester/Saran blends, the two polymers forming these blends being semicrystalline. It was found that Saran is miscible with polycaprolactone (PCL), polyvalerolactone, poly(butylene adipate), and poly(hexamethylene sebacate) since a single glass transition temperature T_g was observed at each composition. However, immiscibility was found between Saran and poly(ethylene adipate), poly-(ethylene succinate), poly(β-propiolactone), and poly(α-methyl-α-n-propyl-β-propiolactone) since two T_g's were recorded at several compositions. Blends were then obtained containing, over a wide range of composition, a miscible amorphous phase and two different types of crystals. From melting-point depression data on PCL and Saran crystals, thermodynamic interaction parameters χ were calculated and found to be different for PCL-rich blends and for Saran-rich blends. This result suggests a variation of χ with composition. Saran is a polymer which does not contain α-hydrogens and its miscibility with polyesters may result from a β-hydrogen bonding interaction or a C?O/C? Cl dipole-dipole interaction.     

Solid-State 13C-NMR detection of the isotropic carbonyl line shape in blends of poly(vinylphenol) with main-chain polyesters

The solid-state NMR isotropic line shape of the carbonyl ¹³C resonance is useful as a qualitative diagnostic probe of the polyester component′s morphology and molecular mobility in partially miscible blends with poly(vinylphenol), PVPh. The main-chain polyesters chosen for investigation in this study are poly(ethylene succinate), poly(ethylene adipate), poly(butylene adipate), and poly(caprolactone). A crystalline phase exists for polyester-rich mixtures in all cases. Verification of this claim is provided by DSC endothermic tran-sitions that map out melting point depression in the temperature-composition phase dia-grams. The carbonyl ¹³C-NMR signal in the crystalline domains exhibits a full width at half height of 1–2 ppm when the glass transition temperature of the blends is below the temperature of the NMR experiment. In all cases, a single concentration-dependent glass-transition temperature is measured by DSC, which increases monotonically from below ambient for polyester-rich blends to well above ambient for blends that are rich in poly(vinylphenol). When the concentration of the amorphous proton donor PVPh is suf-ficient to thwart crystallization of the polyester and increase the glass transition temperature of the blends above the temperature of the NMR experiment, the line width of the carbonyl resonance increases three- to fourfold to ca. 5–6 ppm. When the blends are completely amorphous and T_g is above ambient, the polyester carbonyl ¹³C line shape reveals at least two morphologically inequivalent microenvironments. A partially resolved carbonyl signal in rigid amorphous blends is (a) identified at higher chemical shift relative to the crystalline component, and (b) attributed to hydrogen bonding in the amorphous phase. This inter-action-sensitive hydrogen-bonded carbonyl signal accounts for an increasing fraction of the overall NMR absorption envelope of the carbonyl carbon site when the polyester is saturated with PVPh. The main-chain polyesters were chosen to probe the effect of chemical structure of the proton acceptor on the potential for hydrogen-bond formation. Aliphatic CH₂ spacers between the carbonyl groups dilute the concentration of interacting sites, and the dependence of the carbonyl ¹³C-NMR line shape on blend concentration reveals unique spectroscopic behavior in each of the four blend systems investigated. © 1993 John Wiley & Sons, Inc.     

Thermodynamics of miscible polymer blends using a concentration-dependent χ parameter

The Flory equation-of-state theory, as expressed by Patterson and co-workers, has been applied to two miscible polymer blends: poly(vinyl chloride)/poly(ε-caprolactone) and poly(methyl methacrylate)/poly(vinylidene chloride). For both blends, the variation of the polymer-polymer interaction parameter, χ, as a function of composition, is mostly small and can be accounted for by the Flory theory. However, for poly(vinyl chloride)/poly(ε-caprolactone) blends, at high poly(ε-caprolactone content), the large variation of χ as a function of concentration can be explained by a variation of the surface-to-volume ratio of the polymers in the mixture with blend composition. The variations of the surface-to-volume ratios determined in this study agree with those reported in the literature using small-angle x-ray scattering.     

Melting behavior,miscibility, and hydrogen-bonded interactions of poly(ε-caprolactone)/poly(4-hydroxystyrene-co-methoxystyrene) blends

The miscibility of poly(4-hydroxystyrene-co-methoxystyrene) (HSMS) and poly(ε-caprolactone) (PCL) was investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). HSMS/PCL blends were found to be miscible in the whole composition range by detecting only a glass transition temperature (T_g), for each composition, which could be closely described by the Fox rule. The crystallinity of PCL in the blends was dependent on the T_g of the amorphous phase. The greater the HSMS content in the blends, the lower the crystallinity. The polymer–polymer interaction parameter, χ₃₂, was calculated from melting point depression of PCL using the Nishi-Wang equation. The negative value of χ₃₂ obtained for HSMS/PCL blends has been compared with the value of χ₃₂ for poly(4-hydroxystyrene) (P4HS)/PCL blends. The specific nature, quantitative analysis, and average strength of the intermolecular interactions in HSMS/PCL and P4HS/PCL blends have been determined at room temperature and in the molten state by means of Fourier transform infrared spectroscopy (FTIR) measurements. The FTIR results have been in good correlation with the thermal behavior of the blends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 95–104, 1998     

Lactone polymers. I. Glass transition temperature of poly-ε-caprolactone by means on compatible polymer mixtures

Dynamic mechanical properties determined with a torsion pendulum were used to ascertain the glass transition temperature T_g of poly-ε-caprolactone. By measurements on compatible blends of poly-ε-caprolactone and poly(vinyl chloride), the T_g of amorphous poly-ε-caprolactone was shown to be 202°K at about 1 cps. This is 16°K lower than the T_g of annealed, crystalline polymer. The blend transition data were well fitted by both the Fox and the Gordon-Taylor expressions. The Fox expression was also used to describe the decrease from 233°K of the secondary low-temperature relaxation due to poly(vinyl chloride) by assuming the low temperature relaxation of poly-ε-caprolactone, 138°K, was responsible for the decrease in the blends. The 138°K relaxation due to poly-ε-caprolactone was decreased when more than 50% poly(vinyl chloride) was present.     

Determination of interactions between aryl polyesters and poly(ether imide) via glass transition temperatures of separated phases in immiscible blends

Phase behavior in domains of immiscible blends of poly(pentamethylene terephthalate)/poly(ether imide) (PPT/PEI) and poly(hexamethylene terephthalate)/poly(ether imide) (PHT/PEI) were investigated using differential scanning calorimetry (DSC). The measured glass transition temperature (T _g) reveals that aryl polyesters dissolve more in the PEI-rich phase than the PEI does in the aryl polyester-rich phase, for both PPT/PEI and PHT/PEI systems. Additionally, optical microscopy supports the conclusion that PPT (or PHT) dissolves more in the PEI-rich phase than PEI does in the PPT-rich (or PHT-rich) phase in the aryl polyester/PEI blends. Furthermore, the Flory–Huggins interaction parameters (χ₁₂) for the PPT/PEI and the PHT/PEI blends were calculated to be 0.12 and 0.17, respectively. For the blend systems comprising of PEI and homologous aryl polyesters, the value of χ₁₂ exhibits a trend of variation with respect to structure of aryl polyesters. For the PPT/PEI and PHT/PEI blends, investigated in this study, value of the polymer–polymer interaction parameter (χ₁₂) between the aryl polyester and the PEI was found to be positive, which increases with the number of methylene moieties in the repeating unit of the aryl polyester, ultimately resulting in phase separation observed.     

Fluorescent additive for estimation of compatibility of polyester blend by imipramine-containing polymer

The effects of adding imipramine-containing polymer (PImip-Fl) in two kinds of polyester/lysine triisocyanate (LTI) blends were investigated. PImip-Fl was prepared by Suzuki–Miyaura coupling reaction of dibromoimipramine hydrochloride and dioctylfluorene diboronic acid. The addition of PImip-Fl gave fluorescence to resins [poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL)], and its fluorescent maximum wavelength (λ_max) depended on the resin. PImip-Fl was used as a functional additive for the estimation of compatibility of PLA/PCL blend composite. The addition of LTI to the resins/PImip-Fl blend composites afforded a shorter wavelength shift of the fluorescent λ_max. This suggested that the method using PImip-Fl is adaptive for the estimation of compatibility of the blend composite.     

Prediction of miscibility regions in ternary blends of poly(styrene-stat-acrylonitrile), poly(acrylonitrile-stat-methyl methacrylate), and poly(styrene-stat-methyl methacrylate)

The miscibilities of ternary copolymer blends prepared from poly(styrene-stat-acrylonitrile), poly(styrene-stat-methyl methacrylate), and poly(methyl methacrylate-stat-acrylonitrile) were predicted by calculating the interaction parameter, χ_blend, for various blend combinations, from the corresponding binary segmental interaction parameters estimated from previous work. Binodal and spinodal curves were calculated using the Flory-Huggins theory and it was observed that the most accurate estimate of the boundary between miscible and immiscible blends was given by the spinodal. It has also been demonstrated that in some of the ternary blends with fixed copolymer compositions the miscibility of the blend can be altered by changing the ratio of the three components in the mixture. Conditions for miscibility in this ternary system, and possibly a general feature of all such systems, are (a) that at least two of the binary interaction parameters χ_ij are less than the critical value χ_crit, while the third should not be too much larger, that is, one of the copolymers may act as a compatibilizer for the other two copolymers, (b) that the difference Δχ = /χ₁₂ ? χ₁₃/ is small. © 1992 John Wiley & Sons, Inc.     

Phase Behavior of Polymer Blends

The present report deals with some results on phase behavior, miscibility and phase separation for several polymer blends casting from solutions. These blends are grouped as the amorphous polymer blends, blends containing a crystalline polymer or two crystalline polymers. The blends of PMMA/PVAc were miscible and underwent phase separation at elevated temperature, exhibited LCST behavior. The benzoylated PPO has both UCST and LCST nature. For the systems composed of crystalline polymer poly(ethylene oxide) and amorphous polyurethane, of two crystalline polymers poly(-caprolactone) and poly[3,3,-bis-(chloromethyl) oxetane], appear a single T_g, indicating these blends are miscible. The interaction parameter B's were determined to be –14 J cm^–3, –15 J cm^–3 respectively. Phase separation of phenolphthalein poly(ether ether sulfone)/PEO blends were discussed in terms of thermal properties, such as their melting and crystallization behavior.This revised version was published online in November 2005 with corrections to the Cover Date.     

Micro phase separated epoxy/poly(ε-caprolactone)-block-poly(dimethyl siloxane)-block-poly(ε-caprolactone)/4,4′-diaminodiphenylsulfone systems: Morphology,viscoelasticity, thermo-mechanical properties and surface hydrophobicity

Epoxy resin/4,4′-diaminodiphenylsulfone (DDS) system was modified by the incorporation of poly(ε-caprolactone)-block-poly(dimethyl siloxane)-block-poly(ε-caprolactone) (PCL–PDMS–PCL) triblock copolymer (TBCP). Morphology, viscoelasticity, thermo-mechanical and surface properties of these blends were investigated. All the blends were opaque after curing. PCL blocks of the TBCP were miscible with epoxy resin while the PDMS fraction was immiscible. However in the cured state, both PCL and PDMS blocks were phase separated from epoxy/DDS matrix. The blends exhibited matrix-droplet morphology in which TBCP phase dispersed as spherical domains in epoxy matrix. Addition of TBCP had profound impact on the cure reaction kinetics. Storage modulus and glass transition temperature (T_g) decreased while impact strength significantly increased. Incorporation of 15 phr of TBCP resulted in 80% improvement in impact strength. Further, thermal stability was unaffected while surface hydrophobicity of the blends increased.     

A facile approach to biodegradable poly(ε-caprolactone)-poly(ethylene glycol)-based polyurethanes containing pendant amino groups

A novel biodegradable poly(ε-caprolactone)-poly(ethylene glycol)-based polyurethanes (PCL-PEG-PU) with pendant amino groups was synthesized by direct coupling of PEG ester of NH₂-protected-(aspartic acid) (PEG-Asp-PEG diols) and poly(ε-caprolactone) (PCL) diols with hexamethylene dissocyanate (HDI) under mild reaction conditions and by subsequent deprotection of benzyloxycarbonyl (Cbz) groups. GPC, ¹H NMR, and ¹³C NMR studies confirmed the polymer structures and the complete deprotection. DSC and WXRD results indicated that the crystallinity of the copolymer was enhanced with increasing PCL diols in the copolymer. The content of amino group in the polymer could be adjusted by changing the molar ratio of PEG-Asp-PEG diols to PCL diols. Thus the results of this study provide a good way to prepare polyurethanes bearing hydrophilic PEG segments and reactive amino groups without complicated synthesis.     

The assessment of miscibility and morphology of poly(ε-caprolactone) and poly(para-chlorostyrene) blends

The miscibility and morphology of poly(ε-caprolactone) (PCl) and poly(para-chlorostyrene) (PpClS) blend were investigated by using thermal analysis, morphological analysis, viscometry, and the study of melting point depression. A single glass transition temperature was observed by differential scanning calorimetry (DSC) for PCl/PpClS blends in the whole compositional range (0/100, 25/75, 50/50, 62.5/37.5, 75/25, 90/10). Morphology of the polymers and their blends was studied by scanning electron microscopy (SEM). The Fourier transform infrared spectra of the samples were obtained by spectrometer. Up to 12 cm⁻¹ shifts in carbonyl stretching band of PCl was detected in the spectra of PpClS rich blends. The viscosity of PCl, PpClS and their blends has also been studied to investigate the miscibility according the miscibility criteria Δb, and Δ[η]. Using this data, the interaction parameters α and μ, based on the Chee and Sun et al. approaches were determined. These criteria indicated that the blend is miscible in all proportions up to 90% of PCl content in the blends. The melting point depression of PCl in the blends was examined to obtain the interaction parameter, χ₁₂ for this system. The parameter, χ₁₂ was found to be composition dependent. Negative values of the obtained interaction parameter also support the miscibility of this system up to the 90% PCl in the blend.     

Thermal analysis on phase behavior of poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid) interacting with aliphatic polyesters

Abstract  

Thermal behavior, miscibility, and crystalline morphology in blends of low-molecular-weight poly(l-lactic acid) (LM_w-PLLA) or high-molecular-weight PLLA (HM_w-PLLA) with various polyesters such as poly(butylene adipate) (PBA), poly(ethylene adipate) (PEA), poly(trimethylene adipate) (PTA), or poly(ethylene succinate) (PESu), respectively, were explored using differential scanning calorimeter (DSC), and polarized-light optical microscopy (POM). Phase behavior in blends of PLLA with other polyesters has been intriguing and not straight forward. Using a low- and high molecular weight PLLA, this study aimed at mainly using thermal analyses for probing the phase behavior, phase diagrams, and temperature dependence of blends systems composed of PLLA of two different molecular weights (low and high) with a series of aliphatic polyesters of different structures varying in the (CH₂/CO) ratio in main chains. The blends of LM_w-PLLA/PEA and LM_w-PLLA/PTA show miscibility in melt and amorphous glassy states. Meanwhile, the LM_w-PLLA/PESu blend is immiscible with an asymmetry-shaped upper critical solution temperature (UCST) at 220–240 °C depending on the blend composition. In contrast to miscibility in LM_w-PLLA/PTA and LM_w-PLLA/PEA blends, HM_w-PLLA with polyesters are mostly immiscible; and HM_w-PLLA/PTA blend is the only one showing an asymmetry-shaped UCST phase diagram with clarity points at 195–235 °C (depending on composition). Reversibility of UCST behavior, with no chemical transreactions, in these blends was proven by solvent recasting, gel permeation chromatography, and Fourier transform infrared spectroscopy (FT-IR). Crystalline morphology behavior of the LM_w-PLLA/PEA and LM_w-PLLA/PTA blends furnishes addition evidence for miscibility in the amorphous phase between LM_w-PLLA and PTA or PEA.     

In Situ fibril formation of thermotropic liquid crystal polymer in polyesters blends

Polymer blends based on poly(ethylene 2,6‐naphthalate) (PEN) and poly‐(ethylene terephthalate) (PET) reinforced with a thermotropic liquid crystal polymer (TLCP) were prepared using a melt blending process. Polymer blends consisting of conventional cheap polyester with a small quantity of expensive TLCP are of interest from an economic point of view. The shear viscosity of the TLCP and polyester blends decreased with increasing shear rate and depended on TLCP content. The lower values of the structural viscosity index for the TLCP and polyester blends were attributed to the formation of fibrillar TLCP structures having elongated fibrils in the polyester matrix. The TLCP/PEN blends exhibited long TLCP fibrils that had smaller average diameters and narrower distributions of the diameter compared with those of the TLCP/PET blends. The higher shear force and lower viscosity ratio observed may favor the in situ TLCP fibril formation in the polyester matrix. The viscosity ratio was the most crucial factor in controlling the morphology of the TLCP phase in the TLCP and polyester blends. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3600–3610, 2005     

Sorption phenomena of organic solvents in polymers: Part I

In this work we use the vapor-sorption equilibrium data to show the degree of solvent upturn in each solvent-polymer system. For this purpose, 23 isothermal data sets for four polymer + solvent binaries, one block copolymer + solvent binary and for the corresponding polymer pairs have been used in the temperature range of 25-70 °C. Solvents studied are benzene, carbon tetrachloride, chloroform and pentane. Homopolymers studied are polyisobutylene, poly(ε-caprolactone), poly(ethylene oxide), n-heptadecane, polystyrene, poly(vinyl chloride), poly(vinyl methyl ether), and n-tetracosane.According to these data sets, solvent weight fraction in the polymer is plotted against solvent-vapor activity that is calculated assuming an ideal gas phase of pure solvent vapor neglecting the vapor pressure of the polymer. We use the Flory-Huggins theory to obtain dimensionless interaction parameter, χ. Also the Zimm-Lundberg clustering theory and non-ideality thermodynamic factor, Γ are used to interpret the equilibrium data.     

Thermal Degradation of Poly(ε-caprolactone), Poly(L-lactic acid) and their Blends with Poly(3-hydroxy-butyrate) Studied by TGA/FT-IR Spectroscopy

Summary: The thermal degradation behavior of poly(ε-caprolactone) (PCL) and poly(L-lactic acid) (PLA) have been studied in different environment. It was found that these polymers undergo completely different degradation processes in nitrogen and oxygen atmosphere. In oxygen environment PCL and PLA mainly decompose to CO₂, CO, water and short-chain acids. In nitrogen atmosphere PCL releases 5-hexenioc acid, CO₂, CO and ε-caprolactone, whereas PLA decomposes to acetaldehyde, CO₂, CO and lactide. The polymer blends of poly(3-hydroxybutyrate) (PHB) with PCL and PLA decompose similar to the individual homopolymers with crotonic acid as the initial decomposition product of PHB.     

A verification by FTIR spectroscopy of the effect of some local chain conformations on the specific molecular interactions of solvents,esters, and polyesters with PVC

The molecular interactions of poly(vinylchloride) (PVC) with some solvents [cyclohexanone (CH), methyl ethyl ketone (MEK) and N-methylpirrolidone (MP)], esters [dioctylphthalate (DOP) and butyl stearate (BuSt)], and polyesters [poly(ethylene adipate) (PEA) and poly(ε-caprolactone) (PCL)] have been investigated by FTIR spectroscopy. In all cases the band of the carbonyl group is found to shift to lower frequencies, but significant differences between the solvent and the esters, whether polymeric or not, are evidenced. For PVC-solvent systems, the shift proves to increase linearly as PVC/solvent ratio increases, what suggests that only a definite number of polymer sites is involved. From the slopes of the straight lines this effect of composition is shown to increase in the order MP < MEK < CH, i.e., as the basicity of the solvent decreases. In contrast, for the PVC-esters or polyester blends, a nonlinear behavior consisting of two distinct interaction processes, is obtained. The increase of shift as PVC/ester ratio increases is faster in the first process for all PVC-ester systems and it is particularly enhanced for BuSt and, to a lesser extent, for DOP. Instead, during the second process, that increase is of little significance for BuSt relative to DOP and PCL. These results account for the saturation of the polymer structures that are capable of interacting, at different rates depending on the type of ester. Besides, the whole number of those structures appears to be lower than in the case of solvents. The results are discussed on the ground of, on one side, the mechanism of nucleophilic substitution on PVC, in the same solutions and blends, which, as found previously, is of a stereospecific nature, and, on the other, the electron-donor-acceptor concept (EDA) and the hard-soft-acid-base concept (HSAB) as applied to both the interacting agents (solvents and esters) and the isotactic GTGT and GTTG^? triad conformations as well as the heterotactic GTTT. In the light of the resulting conclusions it is suggested that: (i) the linear behavior shown by the solvents obeys the solvent ability to ensure a dynamic equilibrium between the two possible conformations of - mmr - sequence, i.e., GTGTTT and GTTG^?TT, through the preferential interaction with the little likely GTTG^? conformation, the content of which happens so to be constant as long as there are - mmr - sequences in solution; (ii) the nonlinear behavior of PVC-ester or polyester binary systems reveals a nonequilibrium situation and so the conformational change GTGTTT ? GTTG^?TT, which is highly hindered, will occur occasionally depending on the ester nature. This enables one to attribute the fast and the slow interaction processes to the permanent GTTG^?TT conformations derived from the polymerization and to the same conformations formed as the result of the conformational changes, respectively. Strong support for the above novel finding that PVC … O?C interaction is of a local conformational nature is given by two additional investigations. First, a similar study with a PVC sample prepared at ?50°C, shows that the carbonyl band shifts of CH and PCL are appreciably lower than those of PVC prepared at 70°C. The same holds for the blendof PCL with the latter PVC sample after substitution reaction (0.6%) at ?15°C in CH with sodium benzenethiolate (NaBT). Since the PVC obtained at ?50°C and the 0.6% substituted polymer exhibit a lower content of both permanent GTTG^?TT conformations ad -mmr- sequence, these results agree with expectatins and confirm the above suggestions. Secondly, the changes in the C? Cl stretchign frequencies of PVC with increasing amounts of solvent or ester, as extensively studied, clearly indicate the occurrence of the aforementioned conformational change, and so they are consistent with our proposals as to the actual conformational nature of PVC…O? C interactions. © 1995 John Wiley & Sons, Inc.     

Miscibility and enzymatic degradation studies of poly(ε-caprolactone)/poly(propylene succinate) blends

In the present study the miscibility behaviour and the biodegradability of poly(ε-caprolactone)/poly(propylene succinate) (PCL/PPSu) blends were investigated. Both of these aliphatic polyesters were laboratory synthesized. For the polymer characterization DSC, ¹H NMR, WAXD and molecular weight measurements were performed. Blends of the polymers with compositions 90/10, 80/20, 70/30 and 60/40 w/w were prepared by solution-casting. DSC analysis of the prepared blends indicated only a very limited miscibility in the melt phase since the polymer-polymer interaction parameter χ₁₂ was −0.11. In the case of crystallized specimens two distinct phases existed in all studied compositions as it was found by SEM micrographs and the particle size distribution of PPSu dispersed phase increased with increasing PPSu content. Enzymatic hydrolysis for several days of the prepared blends was performed using Rhizopus delemar lipase at pH 7.2 and 30 °C. SEM micrographs of thin film surfaces revealed that hydrolysis affected mainly the PPSu polymer as well as the amorphous phase of PCL. For all polymer blends an increase of the melting temperatures and the heat of fusions was recorded after the hydrolysis. The biodegradation rates as expressed in terms of weight loss were faster for the blends with higher PPSu content. Finally, a simple theoretical kinetic model was developed to describe the enzymatic hydrolysis of the blends and the Michaelis-Menten parameters were estimated.     

Zein supports scaffolding capacity toward mammalian cells and bactericidal and antiadhesive properties on poly(ε-caprolactone)/zein electrospun fibers

Studies investigate the electrospinnability of poly(ε-caprolactone)/protein blends to produce fibers for tissue engineering applications. However, no reports show that zein can improve the scaffolding capacity toward stem cells and promote antiadhesive and bactericidal properties to the poly(ε-caprolactone)/zein fibers. We create fibers with average diameters ranging from 200 to 400 nm from the electrospinning of poly(ε-caprolactone)/protein mixtures. Poly(ε-caprolactone)/zein blends are electrospinnable at zein concentration between 20 and 40 wt% in a 70/30 formic acid/acetic acid mixture. Water contact angle measurements indicate that zein increases fiber hydrophilicity. The water contact angle decreases from 118° (pure poly(ε-caprolactone) fiber) to 73° for the scaffold containing 40 wt% zein. The zein (40 wt%) significantly increases Young's modulus from 260 MPa (pure poly(ε-caprolactone) fibers) to 980 MPa (poly(ε-caprolactone)/zein fibers) with no substantial influence on elongation at break (ε ≥ 125%) and tensile strength (≥0.040 MPa). The electrospun scaffolds containing zein also promote cell adhesion, proliferation, and spreading of adipose-derived human mesenchymal stem cells for at least 7 days of culture. The zein on poly(ε-caprolactone)/zein fibers can prevent the attachment and proliferation of Escherichia coli and Staphylococcus aureus. We propose these materials for wound healing and skin repair.