Composites Of Poly Research Articles

PEDOT:PSS-Based Wearable Flexible Temperature Sensor and Integrated Sensing Matrix for Human Body Monitoring.

Flexible temperature sensors have been widely used in electronic skins and health monitoring. Body temperature as one of the key physiological signals is crucial for detecting human body's abnormalities, which necessitates high sensitivity, quick responsiveness, and stable monitoring. In this paper, we reported a resistive temperature sensor designed as an ultrathin laminated structure with a serpentine pattern and a bioinspired adhesive layer, which was fabricated with a composite of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)/single-wall carbon nanotubes/reduced graphene oxide (PEDOT:PSS/SWCNTs/rGO) and polydimethylsiloxane (PDMS). The temperature sensor exhibited a high temperature sensitivity of 0.63% °C-1, coupled with outstanding linearity of 0.98 within 25-45 °C. Furthermore, it showed fast response and recovery speeds of 4.8 and 5.8 s, respectively, between 25 and 36 °C. It also demonstrated exceptional stability when subjected to stress and bending disturbances with the maximum bending interference deviation of 0.03%. Additionally, it displayed good cyclic stability over a broad temperature range from 25 to 85 °C, and the standard deviation at 25 °C is 0.14%. A series of experiments including blowing detection, respiratory monitoring with or without a mask, and during rest or sleep were conducted to show the potential of the flexible temperature sensors in human body monitoring. Furthermore, a 4 × 4 flexible temperature sensor matrix was integrated to detect and map objects such as wrenches and blood vessels through human hand skin. The results were consistent with those of infrared measurements. The flexible temperature sensor is capable of real-time temperature monitoring and has the potential in tracking human respiration, assessing sleep quality, and mapping the temperature of various objects.

Effect of carboxymethylated chitosan and cellulose acetate on mechanical properties of PLA blends for biomedical applications

Chitin and chitosan are versatile and valuable biomaterials, with chitosan being abundantly found in the exoskeletons of crustaceans, insects, arthropods, and mollusks. The chemical extraction of chitin involves a series of steps, including deproteinization, demineralization, and decolorization. Chitosan is often combined with various polymeric materials, and polymer blending can enhance the mechanical properties of the resulting bioproduct. In this study, composites of poly(lactic acid) (PLA) with chitosan (Ch) and cellulose acetate (CA) were successfully fabricated using extrusion and injection molding techniques. The chitosan content, ranging from 0 to 7.5 wt. %, was incorporated into the PLA matrix to assess the impact of filler content on the mechanical and morphological properties of the composites. The chitosan powder was first alkalized and then etherified to obtain modified chitosan, specifically o-carboxymethylated chitosan (O-CMCh). The addition of chitosan led to a reduction in tensile strength, flexural strength, modulus of elasticity, and impact strength. However, the hardness of the composite improved with the inclusion of chitosan. The mesoporous structure of chitosan was characterized using nitrogen adsorption and desorption measurements. Morphological analysis revealed that the composite containing 3.75 wt. % chitosan exhibited significantly less fracture surface compared to other composites.

Tailorable piezoelectric and flexoelectric output of a polymer-particle composite

Materials with different combinations of piezoelectric and flexoelectric properties offer multifunctionality and versatility in terms of modes of operation in sensing, actuation, and energy harvesting. We explore a microscopic mechanism for tailoring the macroscopic quasi-static mechanoelectrical output of polymer-particle composites by taking advantage of heterogeneity-induced enhancement of the stress fields and strain gradient fields. The idea focuses on using microscopic inclusions, such as embedded particles and voids, to manipulate the activation and relative contributions of the piezoelectric and flexoelectric effects under different modes of mechanical excitation, such as uniaxial compression and flexural bending. The material system studied is a composite of poly(vinylidene fluoride-co-trifluoroethylene [P(VDF-TrFE)] polymer and nanoaluminum (nAl) particles, or P(VDF-TrFE)/nAl. This system is interesting because P(VDF-TrFE) exhibits both piezoelectric and flexoelectric behaviors and nAl particles have significantly higher elastic stiffness than the polymer. A range of piezoelectric and flexoelectric properties of P(VDF-TrFE) and the stiffness of the particles are considered. Significant microstructural effects are found to enable tailoring of the mechanoelectrical response through microstructure variation. The responses of the composite are quantified using the effective piezoelectric constant (d33,effo) and the effective flexoelectric coefficient (μTR,effo). It is found that the effective macroscopic piezoelectric and flexoelectric behaviors can be changed either independently or simultaneously through different combinations of microstructure attribute changes. The mechanism revealed points out avenues for developing materials with tunable mechanoelectrical behaviors and multifunctionality.

Influence of Carbonyl Iron Particles (CIP) and Glass Microspheres on Thermal Properties of Poly(lactic acid) (PLA).

In this investigation, composite poly(lactic acid) (PLA) systems of hollow glass microspheres (MS) and carbonyl iron particles (CIP) were processed and characterized to investigate the effects of using conductive and insulating particles as additives in a polymer system. PLA-MS and PLA-CIP were set at the two levels of 3.94 and 7.77 vol.% for each particle type to study the effects of the particle material type and loading on neat PLA's thermal properties. It was observed during the twin-screw extrusion that the addition of CIP greatly decreased the viscosity of the PLA melt during processing. Correlations determined using thermogravimetric analysis, differential scanning calorimetry, thermal conductivity, and shear rheology provided insights into how thermal stability was affected. The incorporation of MS and CIP altered thermal properties such as the glass transition temperature (Tg), melting temperature (Tm), and cold crystallization temperature (Tcc). The metal CIP-filled systems had large increases in their thermal conductivity values and viscoelastic transitions compared to those with PLA that were correlated with the observed overheating during extrusion.

Chemiresistive sensor based on PMMA/rGO composite for detection ammonia

Reduced graphene oxide (rGO) has been a promising material in sensing applications. However, rGO-based sensors have very high recovery time at room temperature (RT). Therefore, various materials combination needs to explored to address this issue. We have developed chemiresistive sensor based on a composite of Poly (methyl methacrylate) (PMMA) and rGO for detection of ammonia (NH3). To prepare more oxidized graphene oxide (GO), peroxidation of graphite oxide (PGO) was used from graphite by following Improved Hummer’s Method (IHM). Due to PGO, synthesized rGO was more conductive and high charge capacity. Synthesized PMMA/rGO composite was drop cast on fabricated interdigitated copper electrodes. Various characterization tools were used for materials confirmation. The chemiresistive sensor based on PMMA/rGO exhibited very good sensing behaviour towards NH3 analytes. The range of detection was 1–10 ppm with very good reproducibility. It was far below the Occupational Safety and Health Administration Permissible Exposer Limit (OSHA PEL) of NH3. A chemiresistive sensor based on PMMA/rGO composite revealed better sensing results than a pristine rGO sensor. The response time and recovery time for rGO based sensor was 122 s and 168 s respectively at 2 ppm of NH3 whereas for PMMA/rGO based sensor it was 50 s and 75 s respectively. Moreover, the PMMA/rGO based sensor exhibited repeatability at 2 ppm for NH3 at RT. This type of PMMA/rGO sensor will be very much useful for the detection of hazardous gases in chemical laboratories and industrial areas.

Freeze–Thaw-Induced, Metal Ion Cross-Linked, Mechanically Robust, and Highly Stretchable Composite Poly(vinyl alcohol) Hydrogels for Flexible Electronic Applications

Freeze–Thaw-Induced, Metal Ion Cross-Linked, Mechanically Robust, and Highly Stretchable Composite Poly(vinyl alcohol) Hydrogels for Flexible Electronic Applications

A novel method for improving the electrochemical properties by modifying conductive polymer on 3D printed nanocarbon electrode

The technology of 3D printing has emerged as a potent tool for the preparation of 3D-printed electrode. Using commercial graphene/polylactic acid (PLA) composite filaments as printed materials, fused deposition modeling as 3D-printed technique, 3D printed electrodes (3DEs) were created in this work. Gold nanoparticles (AuNPs) and the composites of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) were used to modify the activated 3DEs for constructing a novel electrode (SACP@Au@3DE), and in this work chlorogenic acid (CGA) was regarded as a probe for testing the performance of SACP@Au@3DE. The surface physicochemical properties of the prepared 3DEs were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The electrochemical properties of the prepared 3DEs were investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods. The constructed SACP@Au@3DE can be used to determine CGA at concentrations ranging from 10 to 400 μM with a limit of detection (LOD) of 4.13 μM. Ultimately, the SACP@Au@3DE sensor was used for CGA detection in coffee powder sample to explore the potential for real sample analysis. This work opens the novel avenue of using conductive polymer modified 3D-printed electrode in the field of sensor.

Bridging biochemistry and microengineering: glucose oxidation in microfluidic biofuel cells with carbon-MEMS and conductive polymers electrodes

Microfluidic biofuel cells are promising power sources for small-scale devices. Its construction is simple and requires low-cost materials. We report four glucose/O2 microfluidic enzymatic biofuel cells consisting in a double-Y-shaped microchannel and based on Carbon Micro Electro Mechanical Systems (C-MEMS) electrodes to test the composite poly(3,4-ethylene dioxythiophene)–poly(gallic acid) (PEDOT-PGAL) conducting polymer as an electroactive layer for enzyme immobilization. The following microfluidic enzymatic biofuel cells were microfabricated to compare their performances: 1) glucose/O2 using bioelectrodes, 2) glucose/O2 using glucose oxidase and Laccase, in solution, 3) glucose/hydrogen peroxide using bioelectrodes, and 4) glucose/hydrogen peroxide using glucose oxidase and horseradish peroxidase, in solution. The use of these two classes of materials, C-MEMS electrodes and conducting polymer inks, offers an advantageous interface for biomolecular electron transfer owing to the rich organic chemistry of the carbon interfaces. On the other hand, the conducting polymer PEDOT-PGAL acts as an electroactive layer for straightforward applications suitable for batch fabrication. All the studied cells presented positive electromotive forces and the discharge behavior of a fuel cell, yielding similar power densities. As expected, the cells that used enzymes in solution delivered higher power densities, but these values are dependent on the flow rate, while cells with immobilized enzymes present a more stable maximum power output. To our knowledge, this is the first report of an electrode system based on pyrolytic carbon/PEDOT-PGAL applied in a microfluidic enzymatic biofuel cell.

Facile design of amphiphobic PVDF membranes utilizing synergy of pore structure and surface fluorination: A demonstration in membrane distillation

Amphiphobic membranes have attracted much attention in membrane distillation (MD) applications, due to its potential in simultaneously resisting membrane wetting and fouling when treating complex wastewater. The current amphiphobic membranes often require non-trivial design of multilevel re-entrant structure. Here we proposed a new class of amphiphobic membranes without multilevel re-entrant surface, by creating a composite poly(vinylidene fluoride)/polyvinyl alcohol/SiO2 membrane with asymmetric structure and well-controlled small surface pores via the NTIPS method, followed by direct fluorination via chemically binding the –OH of polyvinyl alcohol and low surface energy moieties 1H,1H,2H,2H-perfluorodecyl-triethoxysilane, assisted by 3-aminopropyltriethoxysilane and trimesoyl chloride. The amphiphobic membrane showed superior liquid entry pressure above 5 bar with various simulated saline feeds containing surfactants and organic pollutants. The amphiphobic membrane demonstrated robust anti-wetting and anti-fouling performance through a series of 24-h direct contact MD experiments using the above feeds, presenting stable water flux and high rejection, e.g., flux of 50.6 kg/(m2·h) and rejection >99.9 % with feed containing 3.5 wt% NaCl, 1 mM FA, and 2 mM SDS. The results demonstrated the fabrication of robust amphiphobic membrane through simple procedure utilizing the synergy between pore structure and surface chemistry, inspiring more efforts to design adequate membranes for treating complex wastewater.

Synthesis of a Cu-Al bimetallic oxide @ PVDF composite membrane for the degradation of bisphenol a via peroxydisulfate activation: Performance and mechanism

The presence of environmental endocrine-disrupting compounds, such as bisphenol A (BPA), in aquatic environments poses a significant risk to both ecological integrity and human health. Although CuO has been reported as a catalyst for activating peroxydisulfate (PDS) to degrade BPA, it exhibits certain limitations, including low catalytic efficiency, aggregation, and challenges in terms of separation and reusability. In this study, we developed a composite poly (vinylidene fluoride) (PVDF)-based membrane incorporating Cu-Al bimetallic oxide (Cu-Al) to address these issues. Results revealed that when employing the 7 wt% Cu-Al @ PVDF composite membrane to activate 1 mM PDS, approximately 95.3 % of BPA was degraded within 60 min in static experiments. Furthermore, this composite membrane exhibited remarkable efficacy across a broad pH range (3–11) and demonstrated excellent resistance against diverse anionic species. The removal process is proposed to be dominated by electron transfer between the composite membrane, PDS, and BPA via a two-step mechanism: Firstly, electron-rich Cu sites and oxygen vacancies were formed in the composite membrane, facilitating PDS adsorption and electron transfer from Cu sites to PDS to form a ligand complex; subsequently, BPA was adsorbed by the membrane and acted as an electron donor to be oxidized by the ligand complex. As a result, this system showed remarkable selectivity for degrading electron-rich organic compounds with ionization potentials below 9.0 eV. Overall, this work successfully fabricated a catalytic membrane exhibiting efficient PDS activation capability along with selective oxidation performance and facile reusability, making it highly promising for wastewater treatment.

Influence of Process Parameters on the Efficiency of Pervaporation Pilot ECO-001 Plant for Raw Ethanol Dehydration.

Pervaporation is a membrane-based process used for the separation of liquid mixtures. As this membrane process is governed by the differences in the sorption and diffusivities of separated components, close boiling mixtures and azeotropic mixtures can effectively be separated. The dehydration of ethanol is the most common application of hydrophilic pervaporation. The pilot scale properties of hydrophilic composite poly(vinyl alcohol) PVA membrane (PERVAPTM 2200) in contact with wet raw bioethanol are presented. The wet raw bioethanol was composed of ethanol (82.4-89.6 wt%), water (5.9-8.5 wt%), methanol (2.3-6.9 wt%), cyclohexane (0.2-2.4 wt%), higher alcohols (0.2-1.3 wt%), and acetaldehyde (0.004-0.030 wt%). All experiments were performed using a SULZER ECO-001 plant equipped with a 1.5 m2 membrane module. The efficiency of the dehydration process (i.e., membrane selectivity, permeate flux, degree of dehydration) was discussed as a function of the following parameters: the feed temperature, the feed composition, and the feed flow rate through the module. It was found that the low feed flow rate influenced the dehydration efficiency as the enthalpy of evaporation caused a high temperature drop in the module (around 25 °C at a feed flow rate equal to 5 kg h-1). The separation coefficient during pervaporation was in the range of 600-1200, depending on the feed composition. The increase in temperature augmented the permeation flux and shortened the time needed to reach the assumed level of dehydration. It was revealed that dehydration by pervaporation using ECO-001 pilot plant is an efficient process, allowing also to investigate the influence of various parameters on the process efficiency.

Composites of Poly(3-hydroxybutyrate) and Mesoporous SBA-15 Silica: Crystalline Characteristics, Confinement and Final Properties.

Several composites based on poly(3-hydroxybutyrate) (PHB) and mesoporous SBA-15 silica were prepared by solvent-casting followed by a further stage of compression molding. The thermal stability, phase transitions and crystalline details of these composites were studied, paying special attention to the confinement of the PHB polymeric chains into the mesopores of the silica. For that, differential scanning calorimetry (DSC) and real-time variable-temperature X-ray scattering at small angles (SAXS) were performed. Confinement was stated first by the existence of a small endotherm at temperatures around 20 °C below the main melting or crystallization peak, being later confirmed by a notable discontinuity in the intensity of the main (100) diffraction from the mesoporous silica observed through SAXS experiments, which is related to the change in the scattering contrast before and after the crystallization or melting of the polymer chains. Furthermore, the usual α modification of PHB was developed in all samples. Finally, a preliminary investigation of mechanical and relaxation parameters was carried out through dynamic-mechanical thermal analysis (DMTA). The results show, in the temperature interval analyzed, two relaxations, named α and β (the latest related to the glass transition) in order of decreasing temperatures, in all specimens. The role of silica as a filler is mainly observed at temperatures higher than the glass transition. In such cases, stiffness is dependent on SBA-15 content.

Mesoscale model for computational simulation of reaction driven by dielectric breakdown in metal-polymer propellants

The reactivity of heterogeneous energetic materials (HEMs) intimately depends on the underlying microstructural effects. For reactive materials, key factors include the microstructure distribution, morphology, size scale of heterogeneities, reactant mixing, and chemical kinetics of the reactants. We report the development of a mesoscale model for simulating the evolutions of the hotspot field and associated reaction processes when such materials are exposed to external excitations. The model explicitly accounts for microstructure, interdiffusion between the reactant species, advection of the species mixture, and chemical kinetics of the reaction. An Arrhenius relation is used to capture the rate of reactive heat release. The particular material analyzed is a composite of poly(vinylidene fluoride-co-trifluoroethylene) and nanoaluminum [or P(VDF-TrFE)/nAl]. The excitation leading to the initial microstructural temperature increase that kicks off the exothermic reactive processes is the dissipative heating arising from dielectric breakdown under the electric field developed through piezoelectricity and flexoelectricity of P(VDF-TrFE). As such, the model resolves both the breakdown process and the diffusion, advection, and exothermic reaction processes. The evolutions of the temperature and species distribution fields under the combined effects of breakdown and chemistry are used to predict the effects of microstructure, diffusion, and kinetics on several key metrics characterizing the reactive responses of the material. This mesoscale framework admits the quantification of uncertainties in these predicted macroscopic behavior measures due to microstructure heterogeneity fluctuations through the use of multiple, random but statistically equivalent microstructure instantiations. Although the particular hotspot inducing mechanism considered is dielectric breakdown here, the framework can be adapted to analyze reaction initiation and propagation and establish microstructure–reaction behavior relations under other types of hotspot inducing mechanisms, such as thermomechanical inelastic dissipation, frictional heating, and laser or microwave excitation.

Long-lived electrochromic device with protonated viologen and Poly(ethylenedioxythiophene-carbazole)/Prussian blue composite for smart windows

A complementary electrochromic device (ECD) configuration featuring a protonated viologen (VNH2+) as the cathodically coloring electrochrome and a composite of poly(ethylenedioxythiophene-carbazole) (i.e. poly(EDOT-Cz)) and Prussian blue (PB) as the anodically coloring electrochrome marks the first implementation of this innovative high contrast device. A comparative analysis of VNH2+//poly(EDOT-Cz) and VNH2+//poly(EDOT-Cz)/PB ECDs demonstrates a superior integrated visible light transmission modulation (ΔT) of 50.4%, versus 76.7%, higher diffusion coefficient of 4.4 × 10−11versus 3.9 × 10−10 cm2 s−1, higher coloration efficiency (CE) of 424 versus 562 cm2 C−1 (at 550 nm), faster color-bleach switching times of (7.0 and 4.0 s) versus (1.2 and 1.0 s) and a CIE chromaticity coordinate corresponding an intense deep blue state (y: 0.058 versus 0.218) achieved with the composite relative to the pure polymer. The VNH2+//PB ECD also shows lower CE (69 cm2 C−1) and slower coloration-bleaching kinetics (20 and 2 s) compared to the composite based ECD. In addition, long-term cycling stability attained for the VNH2+//poly(EDOT-Cz)/PB ECD, whereby it endures 5000+ color-bleach cycles without showing any major deterioration in optical modulation or switching kinetics underscores the suitability of the composite based ECD for practical smart window applications.

Annular expansion for enhanced orientation and mechanical properties of extruded amorphous PPESK/PES pipes

AbstractWith the discovery of deeper oil fields, conventional metal pumping pipes have been proven to be ineffective in meeting the requirements for deep well oil production due to their high weights and limited corrosion resistance. Therefore, in this study, a composite of Poly(phthalazinone ether sulfone ketone) (PPESK) and polyethersulfone (PES) was used to fabricate nonmetal pipes. To enhance the mechanical properties of the PPESK/PES pipes, a self‐designed annular expansion pipe extruder head was used. The circumferential burst stress and axial tensile strength of the PPESK/PES pipes subjected to 30° expansion were 73.0% and 48.9% higher than those of the unexpanded sample, respectively. When annular expansion was integrated into the extrusion of PPESK/PES/carbon fiber pipes, the axial tensile strength and circumferential burst stress were 45.9% and 88.8% higher than those of the unexpanded sample, respectively. Results of polarized infrared testing and metallographic microscopic examinations demonstrated that molecular chains present a regular orientation at a certain angle to the extrusion direction, under the effect of annular expansion extrusion. These findings highlight the efficiency of annular expansion in promoting the large‐scale production of pipes.

The Influence of Hydroxyapatite Crystals on the Viscoelastic Behavior of Poly(vinyl alcohol) Braid Systems.

Composites of poly(vinyl alcohol) (PVA) in the shape of braids, in combination with crystals of hydroxyapatite (HAp), were analyzed to perceive the influence of this bioceramic on both the quasi-static and viscoelastic behavior under tensile loading. Analyses involving energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) allowed us to conclude that the production of a homogeneous layer of HAp on the braiding surface and the calcium/phosphate atomic ratio were comparable to those of natural bone. The maximum degradation temperature established by thermogravimetric analysis (TGA) showed a modest decrease with the addition of HAp. By adding HAp to PVA braids, an increase in the glass transition temperature (Tg) is noticed, as demonstrated by dynamic mechanical analysis (DMA) and differential thermal analysis (DTA). The PVA/HAp composite braids' peaks were validated by Fourier transform infrared (FTIR) spectroscopy to be in good agreement with common PVA and HAp patterns. PVA/HAp braids, a solution often used in the textile industry, showed superior overall mechanical characteristics in monotonic tensile tests. Creep and relaxation testing showed that adding HAp to the eight and six-braided yarn architectures was beneficial. By exhibiting good mechanical performance and most likely increased biological qualities that accompany conventional care for bone applications in the fracture healing field, particularly multifragmentary ones, these arrangements can be applied as a fibrous fixation system.

Thermal properties of poly(vinyl butyral)/iron oxide composite nanofibers

AbstractIn the present study, iron(II, III) oxide nanoparticles are added to the electrospinning solution of poly(vinyl butyral) in order to yield electrospun composite poly(vinyl butyral)/iron oxide nanofibers. Scanning electron microscopy, energy dispersive x‐ray spectroscopy, and Fourier transform infrared spectroscopy analyses confirm the successful incorporation of iron(II, III) oxide nanoparticles in the nanofibers. Differential scanning calorimetry results show a decrease of approximately 6 °C in the glass transition temperature of the nanofibers with the addition of 1.0 % iron(II, III) oxide nanoparticle compared to neat poly(vinyl butyral) nanofibers. The infrared thermograms suggest the formation of a thermally conductive network for poly(vinyl butyral)/iron oxide nanofibers with faster and more evenly heat dissipation compared to that of neat poly(vinyl butyral) nanofibers while thermal conductivity coefficient of the poly(vinyl butyral) nanofibers is found to increase by 57 % with 1.0 % of nano iron oxide loading. The increased thermal conductivity and thermal absorptivity values suggest the cooling effect of the poly(vinyl butyral)/iron oxide composite nanofibers, which are promising materials for thermal management applications.

Biomimetic aligned nanofibrous dressings containing cell-selective polymer enhance diabetic wound regeneration

Diabetic ulcers remain a significant challenge in wound care due to loss of epithelial cell migration. Aligned nanofibrous scaffolds mimicking the skin's extracellular matrix (ECM) are promising candidates for diabetic wound healing. In this study, a composition of poly(ε-caprolactone), gelatin, and dopamine-containing varying amounts of ε-polylysine (ε-PL) was electrospun to prepare aligned nanofiber wound dressings (ANFDs). We then investigated the morphological, physicochemical, mechanical, and biological properties of fabricated ANDFs. The presence of ε-PL confers bactericidal properties while promoting epithelial and fibroblast adhesion, proliferation, and migration, confirming its cell selectivity. The clinical importance of the ANFDs was then demonstrated in a mice model of full-thickness diabetic wounds. The results confirm that ANFD treatment resulted in a higher rate of wound closure in the linear range of wound closure than wounds treated with silver dressings. Taken together, these results suggest the potential of antimicrobial ANFDs for the treatment of diabetic wounds.

Raman evaluation of the crystallinity degree and composition of poly(L-lactide-co-ε-caprolactone)

In this work, we study two series of the copolymers of L-lactide (LLA) and ε-caprolactone (CL) with the CL molar content of 5, 15, and 30 %. The first series was the commercial semicrystalline granules (Corbion, Netherlands), which we analyzed without any additional modification. The second series was amorphous films, prepared from the granules by hot pressing with the subsequent fast quenching in order to avoid the crystallization. We used Raman spectroscopy in conjunction with the quantum chemical modeling to evaluate the structure of the copolymers. As additional methods, we applied X-ray diffraction (XRD) analysis and differential scanning calorimetry (DSC). The main result of our study is the elaboration of the Raman methods of quantitative analysis of the relative contents of the comonomers and the crystallinity degree of the poly(L-lactide-co-ε-caprolactone). These methods are based on measurements of the ratios of the peak intensities of the poly(L-lactide) (PLLA) bands at 411 and 874 cm−1, the PLLA band at 2947 cm−1 and the poly(ε-caprolactone) band at 2914 cm−1. Raman study shows that growth of the CL content causes the monotonous decrease in the crystallinity degree of PLLA blocks. Density functional theory analysis of LLA decamer in the conformation of helix 103 allows us to assign the PLLA Raman bands. The Raman data on the composition and crystallinity degree of the copolymers correlate very well with the results of XRD and DSC studies, as well as with the information on the composition of the copolymers provided by manufacturer.

A novel functionally graded bilayer membrane with excellent barrier function and in vivo osteogenesis promotion for guided bone regeneration.

Guided bone regeneration (GBR) technology has been widely used as a reliable method to address alveolar bone defects. To improve the clinical effects of GBR approach, there have been attempts to develop barrier membranes with enhanced regenerative properties. However, modifying the material and structure of GBR membranes to integrate physicochemical properties and biological activity remains challenging. The aim of this study was to develop a novel functionally graded bilayer membrane (FGBM) with a gradient structure and composition, and to evaluate its osteogenesis promotion effect for GBR. By combining the phase inversion method and electrospinning method, functionally graded bilayer membranes (FGBM) with gradient structure and composition of poly(lactic-co-glycolic acid) (PLGA), nano-hydroxyapatite (nHA), and gelatin were fabricated in this study. The physicochemical and biological properties of the prepared FGBM, including structural and morphological characterization, mechanical properties, in vitro biodegradation, cell behaviors, and in vivo osteogenic bioactivity, were comprehensively evaluated. The findings demonstrated the successful fabrication of PLGA/nHA/gelatin FGBM with an asymmetric structure, exhibiting enhanced hydrophilic, mechanical, and degradation properties. The incorporation of gelatin not only improved the biological integration, but also enhanced the binding affinity between electrospun fiber layer and phase inversion layer. The FGBM with a 30% nHA mass fraction and a PLGA/gelatin mass ratio of 1:1 exhibited excellent barrier function and osteogenic bioactivities in vitro and in vivo. This work demonstrated the potential of PLGA/nHA/gelatin FGBM in bone regeneration and provided valuable insight for the development of barrier membrane.