Semicrystalline Copolymers Research Articles

Steric Influences on Chain Microstructure in Palladium-Catalyzed α-Olefin (Co)polymerization: Unveiling the Steric-Deficient Effect.

This study addresses the challenge of controlling branching density and branch-type distribution in late-transition-metal-catalyzed chain walking polymerizations. We explored α-diimine Pd(II) complexes with incrementally increased ortho-aryl sterics for long-chain α-olefin (co)polymerization. Pd0-Pd3 catalysts, which feature gradually increased ortho-aryl sterics and at least one small CH3 substituent, exhibited similar 2,1-insertion fractions (44-50%), polymer branching densities (55-63/1000C), and melting temperatures (26-28 °C). In contrast, Pd4 with bulky ortho-aryl sterics covering all sides demonstrated a significant increase in 2,1-insertion fractions up to 82%, leading to "PE-like" polymers with high melting temperatures (Tm > 111 °C). This abrupt change in polymerization behavior, termed the "steric-deficient effect", contrasts with the gradual changes observed in similar Ni(II) systems that we reported previously. Furthermore, due to the rapid chain walking ability of Pd(II) catalysts in long-chain α-olefin (co)polymerization, these catalysts favor the production of polyolefins with higher proportions of methyl branches compared to those produced by Ni(II) catalysts. Particularly, these Pd(II) catalysts are capable of synthesizing functionalized semicrystalline copolymers by copolymerizing 1-octene with a variety of polar comonomers, thereby significantly altering the surface properties of the materials.

Systematic investigations of ortho-aryl substitution effect on chain microstructure in nickel-catalyzed long chain α-olefin polymerization and copolymerization with methyl undecenoate

The tuning of branching density and branch-type distribution of the polyolefin through the ligand modification in “chain-walking”-type late transition metal catalysts is highly desired but remains a significant challenge in olefin polymerization. Herein, we performed a systematic investigation on the (co)polymerization of long chain α-olefin (1-octene and 1-decene) by a series of α-diimine Ni(II) catalysts with the varied ligand sterics arising from the number of the ortho-aryl (4-methylphenyl) substituents. The effects of structural variations, mainly including the steric tuning on the ortho-position of N-aryl ring and ligand backbone, steric distribution (ligand symmetry) tuning and electronic tuning, and polymerization conditions on catalytic activities, polymer molecular weight, polymer branching density, and branch-type distribution were described. The steric effect of ortho-methylphenyl substituents played a major role rather than the electronic effect in determining the preference of insertion fashion (1,2-insertion or 2,1-insertion) and chain walking in long chain α-olefin polymerization. As the bulk and number of ortho-methylphenyl substituents increased, the preferred 2,1-insertion and 1, ω-enchainment (chain straightening) were observed even at high monomer concentrations, thus leading to the decrease of branching density as well as the percentage of methyl branches, and eventually affording the semicrystalline “polyethylene-like” polymer with high Tm up to 121 °C and good mechanical properties. Moreover, the tuning of chain microstructure can be achieved over a very wide range through the modification of ligand sterics. Most importantly, these Ni(II) catalysts could copolymerize long chain α-olefin and polar monomer methyl undecenoate (MU) to generate the various functionalized semicrystalline copolymers with high incorporation ratios of MU up to 11% and Tm in a wide range of 5.6–93 °C.

Amorphous solid dispersions of curcumin in a poly(ester amide): Antiplasticizing effect on the glass transition and macromolecular relaxation dynamics, and controlled release

In order to exploit the pharmacological potential of natural bioactive molecules with low water solubility, such as curcumin, it is necessary to develop formulations, such as amorphous polymer dispersions, which allow a constant release rate and at the same time avoid possible toxicity effects of the crystalline form of the molecule under scrutiny. In this study, polymer dispersions of curcumin were obtained in PADAS, a biodegradable semicrystalline copolymer based on 1,12-dodecanediol, sebacic acid and alanine. The dispersions were fully characterized by means of differential scanning calorimetry and broadband dielectric spectroscopy, and the drug release profile was measured in a simulated body fluid. Amorphous homogeneous binary dispersions were obtained for curcumin mass fraction between 30 and 50%. Curcumin has significantly higher glass transition temperature Tg (≈ 347 K) than the polymer matrix (≈274-277 K depending on the molecular weight), and dispersions displayed Tg’s intermediate between those of the pure amorphous components, implying that curcumin acts as an effective antiplasticizer for PADAS. Dielectric spectroscopy was employed to assess the relaxation dynamics of the binary dispersion with 30 wt% curcumin, as well as that of each (amorphous) component separately. The binary dispersion was characterized by a single structural relaxation, a single Johari-Goldstein process, and two local intramolecular processes, one for each component. Interestingly, the latter processes scaled with the Tg of the sample, indicating that they are viscosity-sensitive. In addition, both the pristine polymer and the dispersion exhibited an interfacial Maxwell-Wagner relaxation, likely due to spatial heterogeneities associated with phase disproportionation in this polymer. The release of curcumin from the dispersion in a simulated body fluid followed a Fickian diffusion profile, and 51% of the initial curcumin content was released in 48 h.

Crystallization behaviour analysis of norbornene based semicrystalline cyclic olefin copolymer (c-COC) for Point-of-care (PoC) device manufacturing

Cyclic Olefin Copolymer (COC) based on norbornene and ethylene is known to be one of the most promising materials for the fabrication of low-cost miniaturized Point-of-care (PoC) devices. Although semicrystalline materials are chemically more resistant and less brittle than amorphous ones, little literature has been reported on the unique semicrystalline COC (c-COC) grade. In this work, a thorough analysis of the crystallization behaviour of a semicrystalline COC (c-COC) is reported for the first time to better understand the relationship between the crystallization and injection moulding processing parameters of the material for the mass manufacturing of PoC devices. The complete thermomechanical characterization carried out by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) for the analysis of the crystallization behaviour suggested that even though a bimodal melting was detected by calorimetry, a unique crystalline structure was detected by X-ray scattering patterns confirming that the crystalline structure generated during the injection moulding of PoC parts is always the same regardless of processing conditions. In non-isothermal crystallization kinetics, the Ozawa model failed describing the crystallization behaviour of the c- COC whereas the combined Avrami-Ozawa and Avrami models successfully described the crystallization behaviour showing an excellent fitting to experimental values and suggesting a three-dimensional growth of nucleus for non-isothermal crystallization.

Dependence of the foaming window of poly(ethylene terephthalate-co-ethylene 2,5-furandicarboxylate) copolyesters on FDCA content

The objective of the present work was to study the dependence of the foaming temperature window of poly(ethylene terephthalate-co-ethylene 2,5-furandicarboxylate) (PEFT) copolyesters on 2,5-furandicarboxylic acid (FDCA) content after different saturation pressures. First, the chemical structure of PEFT copolyesters was characterized, and the effect of FDCA content on the sorption of carbon dioxide (CO2) and the crystallization behavior of PEFT copolyesters was studied. Second, the foaming of PEFT copolyesters was carried out using a batch foaming process. Third, the foaming temperature window was defined for PEFT copolyesters through identifying the lower and the upper foaming temperature boundaries. It was found that with the increase of FDCA content, the sorption of CO2 decreased, and the melting temperature and the crystallinity of PEFT decreased. This led to the increase of the lower foaming temperature while the decrease of the upper one, thus making the foaming temperature window gradually narrowed. It is considered that the lower foaming temperature was determined by the rigidity of the macromolecular chains as well as the CO2 sorption, while the upper one by the crystals formed in PEFT with copolymerization of FDCA units. In addition, with the increase of the saturation pressure, the lower foaming temperature of all PEFT samples decreased, and the upper foaming temperature of PEFT15%, PEFT20% and PEFT30% decreased as well, attributed to the plasticization effect of CO2. However, the upper foaming temperature of PET, PEFT5% and PEFT10% unexpectedly increased with the saturation pressure due to the CO2-induced crystallization. The findings in this study are very important for guiding the foaming and cell structure control, not only for PEFT copolyesters, but also for other semicrystalline copolymers.

Stereocomplexation of Stereoregular Aliphatic Polyesters: Change from Amorphous to Semicrystalline Polymers with Single Stereocenter Inversion.

Stereocomplexation is a useful strategy for the enhancement of polymer properties by the co-crystallization of polymer strands with opposed chirality. Yet, with the exception of PLA, stereocomplexes of biodegradable polyesters are relatively underexplored and the relationship between polymer microstructure and stereocomplexation remains to be delineated, especially for copolymers comprising two different chiral monomers. In this work, we resolved the two enantiomers of a non-symmetric chiral anhydride (CPCA) and prepared a series of polyesters from different combinations of racemic and enantiopure epoxides and anhydrides, via metal-catalyzed ring-opening copolymerization (ROCOP). Intriguingly, we found that only specific chiral combinations between the epoxide and anhydride building blocks result in the formation of semicrystalline polymers, with a single stereocenter inversion inducing a change from amorphous to semicrystalline copolymers. Stereocomplexes of the latter were prepared by mixing an equimolar amount of the two enantiomeric copolymers, yielding materials with increased melting temperatures (ca. 20 °C higher) compared to their enantiopure constituents. Following polymer structure optimization, the stereocomplex of one specific copolymer combination exhibits a particularly high melting temperature (Tm = 238 °C).

Crystallization and molecular mobility in renewable semicrystalline copolymers based on polycaprolactone and polyisosorbide.

A series of novel block copolymers based on two biodegradable polymers, poly(ε-caprolactone), PCL, and poly(isosorbide), PIS, with PIS fractions 5, 10, and 25 wt%, are studied herein. The aim is to assess the effects of the amorphous PIS phase on the properties of the semicrystalline PCL (majority), in addition to the synthesis strategy. The latter involved the polymerization of caprolactone onto initial PIS of low molar mass, resulting, thus, in gradually shorter PCL blocks when the starting amount of PIS is increased. The structure-property relationship investigation, with an emphasis on molecular mobility and crystallization, involves the following sum of complementary techniques: differential scanning calorimetry, dielectric spectroscopy, polarized optical microscopy and X-ray diffraction. The molecular mobility map for these PCL/PIS and initial PIS is drawn here for the first time. Despite the high glass transition temperature of PIS (Tg ∼ 51 °C) compared to that of PCL (-66 °C), the Tg of the copolymers barely changes, as it is mainly ruled by crystallinity. The latter seems to be facilitated in the copolymers, in both the amount and the rate. The local molecular mobility of PCL and PCL/PIS consists of faster γPCL relaxation which is unaffected in the copolymers, whereas the slower βPCL process arising from the backbone ester group rotation exhibits a systematic deceleration in the presence of PIS. A connection between such local motions and the corresponding segmental α relaxation, observed previously in other polyesters, is also found to be true here. Apart from that, the dielectric Tg as well as the cooperativity of the polymer chains drop moderately, which indicates spatial confinement between the PCL crystals, whereas correlations with the looser lamellar chain packing within the spherulites are gained. The relaxations of initial PIS, i.e., γPIS, βPIS and αPIS, could not be resolved within the copolymers. Along with other properties, such as ionic conductivity, we conclude to the homogeneity of our systems, with sufficient PCL/PIS distribution.

Light scattering approach to the in situ measurement of polymer crystallization during 3D printing: A feasibility study

Fused filament fabrication (FFF) is among the most accessible and rapidly developing additive manufacturing (AM) technologies. Even though amorphous thermoplastic polymers are the elected materials in FFF, semicrystalline polymers would enhance the strength and durability of 3D printed parts. The properties of the products depend on the crystalline structure and on the morphology, which develops during the printing process. However, to date, polymer crystallization during 3D printing is still largely unexplored. Then, fundamental knowledge of the crystallization process in realistic printing conditions is necessary to pave the way to semicrystalline polymers in FFF. This work focuses on the implementation of a simple optical setup to follow the crystallization process in situ. The new setup exploits light scattering generated during filament deposition and cooling. To this purpose, the beam scattered by a growing 3D printed wall geometry is collected on a semi-transparent screen during the deposition for both amorphous polylactide and a semicrystalline polyamide copolymer. While the amorphous polymer scatters light anisotropically and generates a vertical scattering pattern, the semicrystalline polyamide produces isotropic scattering. Moreover, the kinetics of scattering intensity increase follows closely that of deposition in the case of polylactide. Instead, it strongly deviates from that for the semicrystalline polyamide. These pieces of evidence suggest that simple light scattering measurements, which are quickly and cost-effectively implemented on a lab-scale, can be further developed to allow a better understanding of polymer structuring phenomena in the highly non-equilibrium conditions of 3D printing.

Analyzing the nanoindentation response of carbon black filled elastomers

AbstractCarbon black (CB) filled elastomers are structurally complex materials that offer unique properties at different length scales. They have tremendous potential applications in a number of fields including the automotive and aerospace industries and for designing innovative smart materials such as artificial muscles but their applications remain limited primarily due to inadequate understanding of their unique mechanical properties. Here, using the Berkovich technique to probe the surface mechanical properties at different scales the nanoindentation response of a series of composites made by homogeneously dispersed CB nanoparticles inside a semicrystalline copolymer matrix has been explored. While the measured loading part of the force–displacement curves is well described by Meyer's empirical power relation, the inverted methodology (IM) approach to deal with the unloading part has been considered and its outcome has been compared with that obtained from the standard Oliver–Pharr's method. The results were consistent with the observed increase of hardness when the applied displacement decreases for all composite samples over a large range of CB volume fraction. Zhang and Xu's model is demonstrated to produce experimentally consistent explanation of this indentation size effect. X‐ray photoelectron spectroscopy (XPS) spectra also show composition gradients with depth up to 100 nm. Furthermore, the effect of CB content, surface features, and length scale‐dependent deformation on the hardness–displacement behavior have been considered. These findings highlight the possibility of attaining a diverse set of mechanical properties by a better understanding of the nanoindentation response of CB filled elastomers which can be useful for material selection and design improvements in a number of practical applications.

Исследование огнезащитных и физико-механических свойств терморасширяющихся уплотнительных лент на основе полиолефиновых термоэластопластов

A study of the flame-retardant (FR) properties, the degree of expansion (DE) and the strength properties of thermally expanding sealing tapes (TST) based on polyolefin thermoplastic elastomers is presented. Experimental TST based on ethylene vinyl acetate rubber (БК-E), and a semi-crystalline copolymer of ethylene and propylene (БК-V) with additives of oxidized graphite (OG) were obtained on laboratory equipment. DE, categories of FR and strength properties of БК-E and БК-V differ slightly. The morphology of the char foams of the obtained compositions was determined. Based on the summary of the results it was found that the composition of БК-E has a better FR in comparison with БК-V. It is estimated that this is primarily due to the nature of the polymer matrix of the compositions, as well as the distribution of components in it, in particular, OG, and their interaction with each other during the combustion process. It is shown that the properties of the developed TST are at the level of the existing ones. A further series of research is expected.

Enabling Oxygen-Sulfur Exchange Reaction to Produce Semicrystalline Copolymers from Carbon Disulfide and Ethylene Oxide.

This work describes the first example of semicrystalline poly(thiocarbonate)s from carbon disulfide (CS2 ) and ethylene oxide (EO), two mass producible low-cost monomers. Lewis acid/base pairs (LPs) exhibit high activity (EO conversion up to >99%, 8h) in catalyzing the copolymerization under low Lewis pair/monomer ratio of 1:1500. Oxygen-sulfur exchange reaction (O-S ER) during the copolymerization of CS2 and EO, the generation and mutual copolymerization with COS, CO2 , and episulfide, is harnessed to introduce crystallizable segments [SC(O)O and SC(S)S] in the copolymer. The type of Lewis base is found to have a great impact on the chain microstructure and the crystalline properties. The formed copolymers with melting point from 117.7 to 245.3°C are obtained. The maximum crystallinity is estimated to be 78% based on the powder wide-angle X-ray diffraction pattern. This work provides a general method to prepare semicrystalline sulfur-containing polymers.

Transport mechanism of lithium ions in non-coordinating P(VdF-HFP) copolymer matrix

Polymer films based on poly(vinylidene difluoride-co-hexafluoropropylene) (P(VdF-HFP)) with different amounts of bis(trifluoromethane)sulfonimide lithium salt (LiTfSI) were prepared from acetone solution in a doctor blade casting machine under controlled and reproducible drying conditions.The modification of the copolymer-based layers show a significant enhancement of conductivity over several orders of magnitude for increasing LiTfSI content and a constantly low electronic conductivity. The addition of salt results in a structural change of the crystalline areas in the semi-crystalline copolymer matrix from α- to γ-phase of P(VdF), which has been studied using Raman spectroscopy and X-Ray diffraction. Lithium ions are coordinated by oxygen atoms of TfSI− as verified by Raman spectroscopy and molecular dynamics simulations. Based on the experimental data and simulation results, we propose a transport mechanism for the lithium ions through salt channels in the amorphous regions of the non-coordinating copolymer matrix via hopping between stabilized positions.

Compartmentalization of therapeutic proteins into semi-crystalline PEG-PCL polymersomes

ABSTRACT Polymersomes are self-assembled nanostructures with high loading capacity, possibility to deliver hydrophilic as well as hydrophobic drugs and stealth characteristic resulting in low immunogenicity. These vesicles can be used to deliver enzyme drugs such as L-asparaginase (ASNase), a first line drug for acute lymphoblastic leukemia treatment. Here, polymersomes based on three semi-crystalline copolymers of poly(ethylene glycol)-b-poly(ε-caprolactone), namely PEG45PCL44, PEG114PCL98, and PEG114PCL114, were investigated for the encapsulation of ASNase, as well as of bovine serum albumin (BSA) as a model protein. Critical aggregation concentration (CAC) of the copolymers was determined by fluorescence spectroscopy and the values varied from 0.6 to 1.26 mg/L. Using film hydration, polymersomes of 200–400 nm and narrow size distribution (polydispersity index values of 0.2–0.3) were obtained when centrifugation was used as a post-film technique. The encapsulation efficiency (EE %) was determined either after centrifugation of the suspension, followed by the proteins measurement in the supernatant or after Size Exclusion Chromatography (SEC) purification, in which the quantification was performed in the eluted fractions corresponding to the free protein. Higher encapsulation efficiency values were obtained after centrifugation (EE% ≈ 20%) in comparison to the measurements after SEC (EE% ≈ 1–5%), indicating that the protein could be partially entrapped in the polymeric network when centrifugation is used as separation method. Nonetheless, this system could provide an initial effect of the free ASNase followed by a long-term effect based on the encapsulated enzyme, leading to decreased dose administration.

Non Isothermal Crystallization Kinetics and Isothermal Decomposition of Poly(Ethylene-Co-Vinylalcohol/Poly(D,L-Lactic-Co-Glycolic Acid) Blend

A series of poly(ethylene-co-vinylalcohol)(PE-VOL)/poly(D,L-lactic-co-glycolic acid (PD,L-LGA) blends with different compositions was prepared by solution casting, and its miscibility was proved through viscosimetry and differential scanning calorimetry (DSC) methods through a positive value of α (San et al. Eq.) and negative value of χ1,2 (Nishi–Wang Equation). XRD analysis of the PE-VOL/PD,L-LGA system revealed a homogeneous distribution of PE-VOL molecules aggregated in the PD,L- LGA matrix and the crystalline structure of the semi crystalline copolymer was conserved in the blend in aggregated form. It also revealed that the amorphous copolymer dispersed in the blend acted as a weak nucleating agent. The non-isothermal crystallization kinetics of neat semi-crystalline copolymer and the blend was used to describe the crystallization process using the Ozawa approach. The thermal stability of these materials was investigated by the thermal gravimetry analysis. The isothermal decomposition of copolymers and their blend were carried out by high resolution mass spectrometry using direct-analysis-in-real-time method. Relevant results that could highlight the miscible character of this blend are revealed through comparison of the different fragments resulting from the decomposition of the blend with those of the pure components.

Tough and ionically conductive polymer electrolyte composites based on random copolymers with crystallizable side chain architecture

Polymer electrolyte composites (PECs) with ionic liquids (ILs), which are also known as ion gels, are fabricated using random copolymers with crystallizable side chain architecture, and the effects of the side chain interactions that establish the physically crosslinked network structure in the PECs are studied. The free radical copolymerization of docosyl acrylates (A22) and tert -butyl acrylates ( t BA) leads to the synthesis of poly( tert -butyl acrylate- r -docosyl acrylate) [poly( t BA- r -A22)] copolymers with a random sequence distribution. The previous studies on semicrystalline copolymer/IL composites have mostly focused on a limited composition range. The poly( t BA- r -A22) random copolymers over a wider range of compositions readily form mechanically tough and ionically conductive PECs upon incorporation of small amounts of IL (approximately 20 wt%). Thin-film transistors with these PECs as an electrolyte gate dielectric exhibit comparable performance to previously reported transistors using PECs with high IL loading. The composition dependence of the side chain crystallization behavior of the random copolymers and the PECs, markedly distinct from that of main chain crystallization, provides a simple and versatile means to design and tune the electrolyte properties for various device applications. • Polymer electrolyte composite comprising semicrystalline copolymers and ionic liquids. • Network formation by random copolymers with crystallizable side chain architecture. • Mechanically tough and ionically conductive electrolyte composite. • Mechanical and electrical properties adjusted by crystallization behavior. • Thin film transistors with polymer electrolyte composites as gate dielectrics.

Polar Thermoplastics with Tunable Physical Properties Enabled by the Stereoselective Copolymerization of Vinyl Ethers

A series of isotactic, semicrystalline vinyl ether copolymers (up to 94% meso diads) were synthesized using a chiral BINOL-based phosphoric acid in combination with a titanium Lewis acid. This stereoselective cationic polymerization enabled the systematic tuning of both glass transition (Tg) and melting temperature (Tm) in copolymers derived from alkyl vinyl ethers (i.e., ethyl, butyl, isobutyl). Additionally, a vinyl ether comonomer bearing an acyl-protected alcohol was utilized as a platform for postfunctionalization. Copolymers containing the masked alcohols were shown to undergo deprotection and subsequent coupling with a desired acid chloride. Collectively, these results highlight the diverse material properties and expanded chemical space accessible through stereoselective cationic polymerization mediated by a chiral anion.

A Near‐Infrared Photoactuator Based on Shape Memory Semicrystalline Polymers toward Light‐Fueled Crane, Grasper, and Walker

AbstractLight‐driven soft actuators with adaptive shape changes, diverse geometric morphing, and reversible macroscopic movements have gained ever‐increasing interest owing to their diverse applications ranging from biomedical to aerospace devices. Herein, presented is a near‐infrared (NIR) light‐stimulated actuator based on cis‐1,4 polybutadiene‐polyethylene semicrystalline copolymer. In the system, a newly synthesized croconaine dye, 2,5‐bis[(6‐(11‐carboxyundecanoate)hexyl‐4‐carboxylate‐piperidylamino) thiophenyl]‐croconium, serves as both an NIR absorbing agent and cross‐linker. Taking advantage of easy processability, two‐way shape memory, and photothermal effects, the actuators thus‐made can undergo intriguing motions in response to NIR irradiation. As a light‐fueled crane, this material shows outstanding heavy‐lift capability; it can lift an item 11 200 times its own weight, and the lifting up/down motions are fully reversible. Besides, the photothermally induced expansion and contraction enables the actuator with reversible bending motions to serve as other remotely controlled soft robots; a light‐driven grasper that can grasp, lift up, lower down, and release an object and a walking robot that can crawl on a ratcheted substrate.

Enhancing the Properties of Poly(ε-caprolactone) by Simple and Effective Random Copolymerization of ε-Caprolactone with p-Dioxanone.

We have developed a straightforward strategy to obtain semicrystalline and random copolymers of ε-caprolactone (CL) and p-dioxanone (DX) with thermal stabilities similar to poly(ε-caprolactone), PCL, but with a faster hydrolytic degradation rate. CL/DX copolymers are promising inks when printing scaffolds aimed for tissue engineering. Such copolymers behave similar to PCL and resorb faster. The copolymers were synthesized by bulk ring-opening copolymerization, achieving a high yield; a molecular weight, Mn, of 57-176 kg mol-1; and an inherent viscosity of 1.7-1.9 dL g-1. The copolymer microstructure consisted of long CL blocks that are separated by isolated DX units. The block length and the melting point were a linear function of the DX content. The copolymers crystallize as an orthorhombic lattice that is typical for PCL, and they formed more elastic, softer, and less hydrophobic films with faster degradation rates than PCL. Relatively high thermal degradation temperatures (above 250 °C), similar to PCL, were estimated by thermogravimetric analysis, and copolymer filaments for three-dimensional printing and scaffolds were produced without thermal degradation.

Effect of semicrystalline copolymers in solid dispersions of pioglitazone hydrochloride: in vitro-in vivo correlation

Objective: The study was aimed to improve the dissolution and bioavailability of developed stable amorphous solid dispersions (SDs) of pioglitazone hydrochloride (PGH), a poorly water-soluble drug. Significance: Poor aqueous solubility of PGH was overcome by the design of SDs. Level A correlation demonstrated between in vitro release and bioavailability of PGH, suggest its biowaiver potential. Methods: The effects of semicrystalline copolymers (poloxamer 407 and gelucire 50/13) and methods of preparations on dissolution behavior, in vivo performance, and stability of PGH SDs were investigated. All the SDs were characterized by FTIR, TGA, DSC, XRD, and SEM. Results: FTIR and TGA showed the compatibility with the polymers. The significant change in melting pattern of the PGH observed in the DSC thermograms supported by XRD patterns & SEM indicated a change from a crystalline to an amorphous state. Gelucire 50/13 was observed to have greater ability to form SDs than poloxamer 407 in solvent evaporation method (SM). Prevention of recrystallization during storage suggested stability of the formulation. Gelucire 50/13 based SD, prepared by SM remarkably increased the dissolution within 15 min (87.27 ± 2.25%) and was supported by dissolution parameters (Q15, IDR, RDR, % DE, f1, f2). These SDs showed pH-dependent solubility. In vivo test showed significantly (p < .05) higher AUC0–t and C max, which were about 3.17 and 4.34 times that of the pure drug respectively. Conclusion: Gelucire 50/13 was found to be a suitable carrier for SM for preparation of SDs of PGH as evident from increased dissolution and bioavailability.

Preparation and characterization of sulfonated semi-crystalline poly(arylene ether)s containing 1,4-FBB moiety as proton exchange membrane fuel cells

Sulfonated semi-crystalline poly(arylene ether)s copolymers containing 1,4-bis(4-fluorobenzoyl)benzene (1,4-FBB), with different degrees of sulfonation (DS), were successfully synthesized via direct polycondensation of 3,3’-disulfonate-4,4’-difluorodiphenylsulfone, bisphenol A, and 1,4-bis(4-fluorobenzoyl)benzene, based on aromatic nucleophilic substitution. The different DS values were realized by controlling the quantity of the sulfonated monomer. The effects of DS on the thermal, mechanical, and oxidative stabilities, water uptake, and ion exchange capacity of the membranes were determined. Compared with Nafion 212®, a state-of-the-art proton-conducting membrane, the block copolymer membrane showed well-separated phase morphology and high proton conductivity at different temperatures. The chemical and phase-separated structures of the copolymers were characterized by proton nuclear magnetic resonance spectroscopy and atomic force microscopy studies. The results showed that semi-crystalline copolymer membranes had acceptable mechanical, thermal, electrochemical, and chemical stabilities. All the above-mentioned results indicate that these semi-crystalline copolymer membranes are good candidate materials for proton exchange membranes.