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Incorporating inorganic particles is a common approach to preparing polymeric materials with desirable physical properties and processability. However, this often results in increased brittleness, necessitating methods to improve melt strength and toughness. In this study, in situ polymerization was employed to functionalize silica nanoparticles with the silane coupling agent (3‐aminopropyl) triethoxysilane (APTES) as a core. A flexible chain segment, poly(butylene itaconate) (PBI), was then introduced as a "rubbery" intermediate layer, resulting in a core‐shell structure of poly(L‐lactic‐co‐butanediol itaconate) nano‐silica copolymer films (PLBISiO2) with both branched and "rubbery" structures. Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) confirmed the formation of macromolecular chains, with the molecular weight (Mn) of PLBI increasing from 59,638 to 74,306 g/mol. This significant increase supports the "rubbery" core‐shell structure. When 0.5% SiO2 was added, the T5% of the film increased by 40°C, significantly improving thermal stability. Additionally, the elongation at break increased to 265.7%, while retaining the original tensile strength. Dynamic rheology experiments further confirmed the generation of branched or "rubbery" core‐shell structures, and a doubling of gas barrier properties was observed with increased silica nanoparticles, suggesting potential applications in food packaging or biopharmaceuticals. Highlights: Nanocomposites with core‐shell structure and improved mechanical properties.Dynamic rheology experiments confirmed the formation of the core‐shell structure.Significantly improved gas barrier properties due to core‐shell structure. [ABSTRACT FROM AUTHOR]

The treatment of water containing oil from various industrial and environmental sources is a challenging issue. Polymeric composite membranes with reinforcing fillers have been extensively used to overcome this issue. In this study, poly(L-lactic acid) (PLLA) incorporated with eggshell powder (ESP) composite membranes were prepared to absorb oil in water. ESP has been modified into silane-treated ESP (SESP) by using the silane coupling agent, 3-(methacryloyloxy)propyl trimethoxysilane (MPTS) to enhance the compatibility of the ESP in the membrane. The concentration of MPTS solution used to treat the ESP has been varied at 1%, 3% and 5% denoted as SESP1, SESP3, and SESP5, respectively to observe the chemical and mechanical properties of the composite membrane. Composite membranes reinforced with SESP have high deformation resistance with a modulus value of 2105.45 MPa compared to 1892.77 MPa of PLLA membrane. At 5% MPTS concentration, the membrane's water contact angle (WCA) increased to 75°. The oil absorption ability of the composite membrane filled with SESP5 increased from ~ 14% to 71%. The use of MPTS to modify the surface of the ESP has improved the compatibility between the reinforcing filler and the polymer matrix as well as with the oil absorption capability. [ABSTRACT FROM AUTHOR]

The melt-crystallization, cold-crystallization, melting behaviors, thermal stability, and optical properties of poly(L-lactic acid) (PLLA) nucleated by a phenylacetic hydrazide derivative (DAPH) were investigated. The melt-crystallization confirmed DAPH’s heterogeneous nucleation role in improving PLLA’s poor crystallization capability, concurrently DAPH loading, cooling rate and final melting temperature were three key factors affecting PLLA’s melt-crystallization behaviors. The results from cold-crystallization indicated that the addition of DAPH could accelerate PLLA’s cold-crystallization via cold-crystallization peak’s shift toward the lower temperature side as DAPH loading increased. Through analysis of PLLA/DAPH’s multiple melting behaviors after melt-crystallization, it was found that DAPH loading, the previous melt-crystallization and heating rate determined PLLA/DAPH’s melting processes after melt-crystallization; and PLLA/DAPH’s melting processes after isothermal crystallization depended on the previous crystallization temperature. A drop in thermal decomposition temperature for 5 wt.% mass loss suggested that pure PLLA has better thermal stability compared with PLLA/DAPH. Additionally, the introduction of DAPH could not improve PLLA’s transparency, in contrast, the haze of PLLA was increased greatly owing to the existence of DAPH.

Cough is a common symptom of various respiratory diseases. However, recognizing a subject's cough using acoustic imaging can be challenging due to the complexity of coughing and the vulnerability of acoustic acquisition to external interference. This research aims to address these issues by utilizing a flexible piezoelectric ionic liquid‐doped poly(L‐lactic acid) (PLLA) sensor to gather the pressure signals from the human surface. 1‐butyl‐3‐methylimidazolium bis (trifluoromethylsulfonyl)imide ([BMIm]TFSI) ionic liquid (IL) can enhance the piezoelectric performance of PLLA thin film, the corresponding output voltage, and impact sensitivity are improved to three times and 105.1% for the PLLA/IL thin film with 1 wt% IL, 140 °C annealing 2 h and four times drawing ratio. The effect of IL on the crystallization behavior and piezoelectric properties of thin films during their preparation is investigated. The flexible PLLA/IL sensor is integrated into a wearable electronic system which collects and transmits piezoelectric signals from cough‐induced vibrations to the filter for denoising, then the acquired cough data are decomposed using the Empirical Mode Decomposition method and trained in a multi‐layer perception model to detect human coughing. It's evident that the flexible piezoelectric PLLA/IL sensors can be applied to human coughing recognition and show great potential applications in intelligent healthcare. [ABSTRACT FROM AUTHOR]

This study investigates the biodegradation behavior of a blend of poly(L-lactic acid) (PLLA) and amorphous polyhydroxyalkanoate (aPHA) (50:50 wt%) under seawater conditions for 12 weeks at 30 °C. The results revealed that the inclusion of aPHA in the blend enhanced the biodegradation of PLLA. The average molecular weight analysis indicated that the blend underwent homogeneous degradation primarily through exo-chain scission. Morphological changes observed via scanning electron microscopy demonstrated that aPHA first underwent decomposition in the blend, creating channels within PLLA that enhanced water and microorganism contact and promoted PLLA hydrolysis. The release of low-molecular-weight acids from the aPHA decomposition further facilitated PLLA hydrolysis. The graph depicts fluctuations in the weight-average molecular weight of PLLA, the PLLA/aPHA blend, and aPHA throughout the biodegradation period under seawater conditions. [ABSTRACT FROM AUTHOR]

Plastics have remained the best choice for fruit and vegetable packaging due to their exceptional transparency, flexibility, optional good barrier and cost‐effectiveness. However, a large number of plastics end up in the environment after serving their intended purpose and persist there for centuries. Since worldwide attention to environmental issues has become an irreversible historical trend, cost‐effective renewable biodegradable packaging material is highly desirable for the packaging industry to satisfy both industrial demands as well as consumer expectations. Poly (L‐lactic acid) (PLLA), a renewable biodegradable polymer derived from biomass, has been widely studied as a very attractive polymer for food packaging applications. However, its brittle nature and medium CO2/O2 permeability are not friendly for its utilisation in the aspect of fresh agricultural products packaging. In such a context, great efforts have been devoted to improvements in the mechanical and permeability of PLLA to meet the requirements of food packaging. The main purpose of the review is to summarise the mechanical and permeability properties of composite films developed by the incorporation of toughness reinforcing agents into the PLLA matrix. The elongation at break of PLA can be increased up to 250 times by modification, and the CO2 permeability of PLA can be increased by 2–3 times by modification. We also elaborate on studies of the preservation effect of PLLA composite films on fresh fruits and vegetables. [ABSTRACT FROM AUTHOR]

This study focused on the poly(L-lactic acid) (PLLA) polymer matrices by adding branched polyethyleneimine (PEI) as an aminolysis agent. Electrospun nanofibers were made by blending PLLA and PEI at various weight ratios (85-15, 75-15, and 65-35) and mixing times (0.5 h, 1 h, and 2 h). Amine groups were introduced into the nanofiber matrices, as confirmed by Fourier-transform infrared (FTIR) spectroscopy. The PLLA-PEI reaction was affected by mixing time, as shown by rheological measurements of absolute viscosity and surface tension. As a result, the nanofiber diameters decreased up to 42% and 89% with longer mixing time and higher PEI content, respectively. The aminolysis reaction rate increased up to 6.6 times with more PEI. Furthermore, the nanofibers had improved host-guest interactions, as demonstrated by contact angle, drug release, dye adsorption and water adsorption tests. The drug-loading capacity of the nanofibers was enhanced by PEI modification, as indicated by the release profile of tetracycline hydrochloride. The nanofibers also revealed more than 99.99% antibacterial activity due to the presence of the amine groups in PEI. Optimum mixing time and polymer ratio were proved to be substantial parameters to reach appropriate nanofiber and improve spinnability for further biomedical applications. [ABSTRACT FROM AUTHOR]

Abstract L‐ and D‐ form oligo(lactic acid)s (OLLA and ODLA) grafted α‐cellulose (OLLA‐g‐cellulose and ODLA‐g‐cellulose) were prepared by the graft polycondensation reaction in C6H5CH3 medium at 130°C and 380 mm of mercury pressure. Para‐toluene sulphonic acid (5 wt% of oligo(lactic acid)) was used as a catalyst whereas potassium persulfate (0.01 wt% of oligo(lactic acid)) was used as a co‐catalyst in the graft polycondensation reaction. OLLA and ODLA with a degree of polymerization (DP) 6–7 used in polycondensation reaction were also prepared by ring‐opening polymerization of L‐ and D‐lactides at 140°C for 10 h with stannous octoate (C16H30O4Sn) as a motivator, L, and D monomer of lactic acids as co‐motivators. FTIR analysis proved the bonding of OLLA and ODLA onto the α‐cellulose surface. The thermal properties of poly(L‐lactic) acid (PLLA) composites were explored by thermal analysis (TG, DTA, and DTG). Degradation, melting, and maximum weight loss temperature of the composites were increased with the increase of grafted cellulose up to 10% and then decreased. TG and DTA results showed that the incorporation of grafted α‐cellulose (grafted cellulose) can improve the thermal properties of PLLA composites. Highlights Synthesis of oligo(lactic acid)s from L‐ and D‐lactides by ring‐opening polymerization reactions. α‐cellulose extraction and graft modification with oligo(lactic acid)s. Preparation of grafted α‐cellulose composite with PLLA matrix. Evaluation of thermal properties of the grafted α‐cellulose‐reinforced composites.

Nerve injuries pose a drastic threat to nerve mobility and sensitivity and lead to permanent dysfunction due to low regenerative capacity of mature neurons. The electrical stimuli that can be provided by electroactive materials are some of the most effective tools for the formation of soft tissues, including nerves. Electric output can provide a distinctly favorable bioelectrical microenvironment, which is especially relevant for the nervous system. Piezoelectric biomaterials have attracted attention in the field of neural tissue engineering owing to their biocompatibility and ability to generate piezoelectric surface charges. In this review, an outlook of the most recent achievements in the field of piezoelectric biomaterials is described with an emphasis on piezoelectric polymers for neural tissue engineering. First, general recommendations for the design of an optimal nerve scaffold are discussed. Then, specific mechanisms determining nerve regeneration via piezoelectric stimulation are considered. Activation of piezoelectric responses via natural body movements, ultrasound, and magnetic fillers is also examined. The use of magnetoelectric materials in combination with alternating magnetic fields is thought to be the most promising due to controllable reproducible cyclic deformations and deep tissue permeation by magnetic fields without tissue heating. In vitro and in vivo applications of nerve guidance scaffolds and conduits made of various piezopolymers are reviewed too. Finally, challenges and prospective research directions regarding piezoelectric biomaterials promoting nerve regeneration are discussed. Thus, the most relevant scientific findings and strategies in neural tissue engineering are described here, and this review may serve as a guideline both for researchers and clinicians.

Electrospun fibre has shown great potential in tissue engineering and regenerative medicine due to its high specific surface area and extracellular matrix-mimicking structure. However, fabricating an electrospun fibrous scaffold with controllable complex 3D macroscopic configuration remains a challenge. In the present study, a novel method was designed to transform 2D electrospun poly (L-lactic acid) (PLLA) fibrous membrane to tubular PLLA fibrous scaffolds with 3D complex but tailored configuration. The electrospun PLLA fibrous membrane was rolled around a designed mould and then treated with acetone. Treated vascular grafts’ length, diameter, and shape can be tailored by the mould parameters. Moreover, treated vascular grafts achieve favourable mechanical properties (Young’s modulus = 155 MPa, tensile stress = 8.79 MPa and radial force = 2.2 N) and the mechanical properties could be engineered on demand. In addition, treated vascular grafts kept their initial structure and size during long-term in vitro experiments once they were formed. In addition, with the acetone-induced recrystallization of PLLA, pristine solid PLLA fibres were changed to hierarchical porous PLLA fibres with ultra-high specific surface area (28.9 m2/g) and wettability (water contact angle = 101.32°), which has positive effects on cell adhesion and proliferation ability. A7r5 in vitro experiment shows that the proliferation rate of treated vascular grafts increased 153% at day 4 and 170.6% at day 7 compared with pristine vascular grafts.

L‐ and D‐ form oligo(lactic acid)s (OLLA and ODLA) grafted α‐cellulose (OLLA‐g‐cellulose and ODLA‐g‐cellulose) were prepared by the graft polycondensation reaction in C6H5CH3 medium at 130°C and 380 mm of mercury pressure. Para‐toluene sulphonic acid (5 wt% of oligo(lactic acid)) was used as a catalyst whereas potassium persulfate (0.01 wt% of oligo(lactic acid)) was used as a co‐catalyst in the graft polycondensation reaction. OLLA and ODLA with a degree of polymerization (DP) 6–7 used in polycondensation reaction were also prepared by ring‐opening polymerization of L‐ and D‐lactides at 140°C for 10 h with stannous octoate (C16H30O4Sn) as a motivator, L, and D monomer of lactic acids as co‐motivators. FTIR analysis proved the bonding of OLLA and ODLA onto the α‐cellulose surface. The thermal properties of poly(L‐lactic) acid (PLLA) composites were explored by thermal analysis (TG, DTA, and DTG). Degradation, melting, and maximum weight loss temperature of the composites were increased with the increase of grafted cellulose up to 10% and then decreased. TG and DTA results showed that the incorporation of grafted α‐cellulose (grafted cellulose) can improve the thermal properties of PLLA composites. Highlights: Synthesis of oligo(lactic acid)s from L‐ and D‐lactides by ring‐opening polymerization reactions.α‐cellulose extraction and graft modification with oligo(lactic acid)s.Preparation of grafted α‐cellulose composite with PLLA matrix.Evaluation of thermal properties of the grafted α‐cellulose‐reinforced composites. [ABSTRACT FROM AUTHOR]

We present synthetic experiments of lactic acid (LA) polycondensation to produce poly(lactic acid) (PLA) as well as kinetic modeling calculations that capture the polymer molecular weight increase with time, given the initial concentrations. Tin-octoate-catalyzed polycondensation of (D,L)- or L-lactic acid was carried out in pre-dried toluene after azeotropic dehydration for 48–120 h at 130–137 °C. The polymerization was optimized by varying lactic acid and catalyst concentrations as well as the temperature. Gel permeation chromatography was used to experimentally follow the evolution of molecular weights and the products were characterized by NMR, TGA, DSC and IR. Under optimal conditions, PLLA with weight-average molecular weight (Mw) of 161 kDa could be obtained. The rate equations that describe polycondensation kinetics were recast in a condensed form that allowed very fast numerical solution and calculation of the number-average molecular weight with time. Deviations with respect to the experiment were minimized in a least-squares fashion to determine rate constants. The optimized kinetics parameters are shown to reproduce the experimental data accurately. [ABSTRACT FROM AUTHOR]

This review will briefly examine the development of 3D‐printed scaffolds for craniofacial bone regeneration. We will, in particular, highlight our work using Poly(L‐lactic acid) (PLLA) and collagen‐based bio‐inks. This paper is a narrative review of the materials used for scaffold fabrication by 3D printing. We have also reviewed two types of scaffolds that we designed and fabricated. Poly(L‐lactic acid) (PLLA) scaffolds were printed using fused deposition modelling technology. Collagen‐based scaffolds were printed using a bioprinting technique. These scaffolds were tested for their physical properties and biocompatibility. Work in the emerging field of 3D‐printed scaffolds for bone repair is briefly reviewed. Our work provides an example of PLLA scaffolds that were successfully 3D‐printed with optimal porosity, pore size and fibre thickness. The compressive modulus was similar to, or better than, the trabecular bone of the mandible. PLLA scaffolds generated an electric potential upon cyclic/repeated loading. The crystallinity was reduced during the 3D printing. The hydrolytic degradation was relatively slow. Osteoblast‐like cells did not attach to uncoated scaffolds but attached well and proliferated after coating the scaffold with fibrinogen. Collagen‐based bio‐ink scaffolds were also printed successfully. Osteoclast‐like cells adhered, differentiated, and survived well on the scaffold. Efforts are underway to identify means to improve the structural stability of the collagen‐based scaffolds, perhaps through mineralization by the polymer‐induced liquid precursor process. 3D‐printing technology is promising for constructing next‐generation bone regeneration scaffolds. We describe our efforts to test PLLA and collagen scaffolds produced by 3D printing. The 3D‐printed PLLA scaffolds showed promising properties akin to natural bone. Collagen scaffolds need further work to improve structural integrity. Ideally, such biological scaffolds will be mineralized to produce true bone biomimetics. These scaffolds warrant further investigation for bone regeneration. [ABSTRACT FROM AUTHOR]

Poly(L-lactic acid) (PLLA), a biodegradable polymer from plant sources, is widely employed in biomedical applications for its biocompatibility and versatile mechanical properties. However, comprehending its phase behavior in various solvents poses a challenge for broader applications. In this study, the phase behavior of the polymer was investigated in various solvent and cosolvent media and combinations at a wide range of temperatures and pressures to gain insight into the polymer properties. PLLA of varying intrinsic viscosity (IV): [0.15 dl/g, with an estimated weight average molecular weight (Mw) range of approximately: 1600 to 2400 g/mol; 1.0 dl/g (Mw): 100,000 g/mol); and 1.8 dl/g (Mw): 80,000 to 100,000 g/mol] was employed for this study. The phase behavior of the polymer across different compositions of PLLA and solvent (CH2F2, CHF3, CO2, DME, F-22) in a wide range of temperatures from 333 to 425 K and high pressure 1.55 to 172 MPa was investigated. Miscibility of PLLA in DME and F-22 is predicted to be higher with increasing in concentration than the other cosolvents. Furthermore, in the case of the supercritical solvent CHF3 and DME the phase transition pressure curve of PLLA was observed to exhibit a lower critical solution temperature (LCST) type with a positive gradient with increasing temperature. However, lower phase transition pressure was noticed for lower molecular weight PLLA in supercritical solvent CHF3 and DME, i.e., of the order IV 0.15 dl/g

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Poly(L-lactic acid) (PLLA) and PLLA/gelatin polymers were prepared via electrospinning to evaluate the effect of PLLA and gelatin content on the mechanical properties, water uptake capacity (WUC), water contact angle (WCA), degradation rate, cytotoxicity and cell proliferation of membranes. As the PLLA concentration increased from 1 wt% to 3 wt%, the tensile strength increased from 5.8 MPa to 9.1 MPa but decreased to 7.0 MPa with 4 wt% PLLA doping. The WUC decreased rapidly from 594% to 236% as the PLLA content increased from 1 to 4 wt% due to the increased hydrophobicity of PLLA. As the gelatin content was increased to 3 wt% PLLA, the strength, WUC and WCA of the PLLA/gelatin membrane changed from 9.1 ± 0.9 MPa to 13.3 ± 2.3 MPa, from 329% to 1248% and from 127 ± 1.2° to 0°, respectively, with increasing gelatin content from 0 to 40 wt%. However, the failure strain decreased from 3.0 to 0.5. The biodegradability of the PLLA/gelatin blend increased from 3 to 38% as the gelatin content increased to 40 wt%. The viability of L-929 and MG-63 cells in the PLLA/gelatin blend was over 95%, and the excellent cell proliferation and mechanical properties suggested that the tunable PLLA/gelatin barrier membrane was well suited for absorbable periodontal tissue regeneration. [ABSTRACT FROM AUTHOR]

Copyright of Polymer Materials Science & Engineering is the property of Sichuan University, Polymer Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Objective The primary objective of this research was to develop a poly(l‐lactic acid) (PLLA) scaffold and evaluate critical characteristics essential for its biologic use as a craniofacial implant. Materials and Methods PLLA scaffolds were designed and fabricated using fused deposition modeling technology. The surface morphology and microarchitecture were analyzed using scanning electron microscopy (SEM) and microCT, respectively. Crystallography, compressive modulus, and the piezoelectric potential generated upon mechanical distortion were characterized. Hydrolytic degradation was studied. MG63 osteoblast‐like cell proliferation and morphology were assessed. Results The porosity of the scaffolds was 73%, with an average pore size of 450 µm and an average scaffold fiber thickness of 130 µm. The average compressive modulus was 244 MPa, and the scaffolds generated an electric potential of 25 mV upon cyclic/repeated loading. The crystallinity reduced from 27.5% to 13.9% during the 3D printing process. The hydrolytic degradation was minimal during a 12‐week period. Osteoblast‐like cells did not attach to the uncoated scaffold but attached well after coating the scaffold with fibrinogen. They then proliferated to cover the complete scaffold by Day 14. Conclusion The PLLA scaffolds were designed and printed, proving the feasibility of 3D printing as a method of fabricating PLLA scaffolds. The elastic modulus was comparable to that of trabecular bone, and the piezoelectric properties of the PLLA were retained after 3D printing. The scaffolds were cytocompatible. These 3D‐printed PLLA scaffolds showed promising properties akin to the natural bone, and they warrant further investigation for bone regeneration.

Copyright of Polymer Materials Science & Engineering is the property of Sichuan University, Polymer Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The inherent weak crystallization capacity has an impact on the processability and serviceability of poly(lactic acid) (PLA) and limits its application. D‐mannitol (DM) and xylitol (Xy), acting as a nucleation accelerant, were melt‐blended with poly(L‐lactic acid) (PLLA) and the nonisothermal crystallization behavior was investigated. At 1% dosage, the crystallization temperatures of polyol‐modified PLLAs are 10–15°C higher than those of neat PLLA in the cooling rate range of 5–20°C. The theoretical half‐time of crystallization (t1/2) of the Jeziorny model remains constant over the cooling rate range of 10–20°C min−1, in contrast to the greatly reduced t1/2 reported for heterogeneous nucleating agents. Xy is more effective than DM in promoting crystallization. It increases the crystallinity of PLLA to ~40% within the 1%–5% dosage; and the activation energy of nonisothermal crystallization calculated by the Friendman method follows the order of magnitude: neat PLLA ˃ PLLA/DM ˃ PLLA/Xy. Polyols promote the crystallization of PLLA by a mechanism different from heterogeneous nucleation, providing an efficient and biosafety approach to improve the performance of PLA. [ABSTRACT FROM AUTHOR]

In this study, we utilized and modified ISO 14855-2, an industrial composting test, as a basis for conducting biodegradation tests on the poly(l-lactic acid) (PLLA)/amorphous polyhydroxyalkanoate (aPHA) blends under different conditions. Based on the obtained results, our objective was to investigate the reasons behind the biodegradability of PLLA under home composting conditions when blended with other materials. The compatibility of aPHA with PLLA in the blend interferes with the crystallization of PLLA via microphase separation, ultimately resulting in a dominantly amorphous PLLA structure. Additionally, the microphase separation of the two polymers created microfluidic channels by aPHA, which increased the surface area accessible to microorganisms in the compost, facilitating the biodegradation of both polymers. Furthermore, low-molecular-weight acids generated from aPHA contribute to the autocatalytic effect, further promoting biodegradation. Therefore, blending PLLA with aPHA has the potential to improve the biodegradability of PLLA and widen its range of applications.

Blends of poly(L-lactic acid)/nanoparticle silver and GTA (plasticizer) are present, and the crystallization effect was studied. The effect of the crystallization was investigated by oxygen permeability, isothermal crystallization, and mechanical behavior. Observed properties varied according to the concentration of Ag-NP (0.025–0.1%) dispersed in the continuous phase PLLA. Overall isothermal crystallization rates of the PLLA nanocomposites were higher than those of neat PLLA due to the nucleating effect of the Ag-NP and the enhanced chain mobility caused by the plasticizer (GTA). Ternary blends exhibited an improvement in toughness compared to PLLA alone. Also, the effect is due to the α and αʹ crystals growing up, as observed by XRD. The films exhibited a high barrier of oxygen permeability from 2118 to 18 cc·mm/m2·d, 99% lower than that of PLLA (or 117 times lower), Ag-NP concentration (0.1%) dispersed in the polymer with GTA as a plasticizer. [ABSTRACT FROM AUTHOR]

A ternary blend of poly(L-lactic acid) (PLA), poly(ε-caprolactone) (PCL) and poly(vinyl acetate) (PVAc) was melt compounded with an aim to obtain novel biodegradable blends with a balance of performance. We systematically studied the relationship between the microstructure and macroscopic properties of the ternary blends. PVAc was miscible with both PLA an PCL. It was interesting that PVAc was selectively located in the PLA matrix of PLA/PCL/PVAc ternary blends, which significantly affected the crystallization behavior, mechanical and rheological properties, and enzymatic hydrolysis rate of the blends. The inhibited crystallization of PLA was achieved, whereas the crystallization of PCL was not affected by incorporating PVAc. Unexpectedly, increases of 10%, 17% and 26% were achieved in the yield strength, breaking strength and modulus of the ternary blend with 20 wt% PVAc compared to PLA/PCL binary blend, while the elongation at break maintained above 300%. Moreover, the rheological properties was enhanced and enzymatic hydrolysis rate was decelerated by introduction of PVAc. The excellent stiffness − toughness balance coupled with the enhanced melt viscoelasticity of the blends will help to expand the property range and processing methods of biodegradable polymers. [ABSTRACT FROM AUTHOR]

Spinal cord injury (SCI) treatment remains a worldwide challenge considering its limited self-repair capacity. The transplantation of neural stem cells (NSCs) has been proposed as a potential approach to restoring neurological function by promoting axonal regeneration. While nanofibrous biomaterials provide the biomimetic microenvironment for the immobilization and growth of transplanted NSCs. In this study, a biomimetic poly-(polyol sebacate)-based elastomeric nanofibrous scaffold developed with poly-(l-lactic acid) (PLLA) and poly-(polycaprolactone triol-co-sebacic acid-co-BES sodium salt) (PPSB) was fabricated by electrospinning and combined with human NSCs (hNSCs) for SCI treatment. The electrospun PLLA/PPSB nanofibrous scaffold containing 40 wt % PPSB demonstrated a highly porous microstructure, sulfonate group modification, strong hydrophilicity, suitable degradation performance, and good mechanical properties. The scaffold promoted the proliferation and further differentiation of hNSCs into neuronal cells. Moreover, the transplantation of hNSCs-loaded PLLA/PPSB nanofibrous scaffold attenuated the inflammatory response, enhanced the regeneration of neurons, and inhibited the growth of astrocytes in the lesion areas, thereby promoting the functional restoration of the spinal cord in rats with completely transected SCI. Thus, we conclude that the hNSCs-loaded PLLA/PPSB composites could promote the repair of spine cord injury. The findings could provide insight into the combined treatment strategies for SCI based on NSCs and bioactive biomaterials. [ABSTRACT FROM AUTHOR]

Shear mode guided waves are highly demanded for underwater structural health monitoring (SHM) applications due to their simplified non‐dispersive feature and minimal acoustic energy loss in the presence of liquid. Excitation and detection of pure shear wave are challenging using conventional piezoelectric materials used in the current ultrasonic transducers because they have complex piezoelectric responses mixed with multiple longitudinal, transverse, and shear modes. They also suffer from aging issue due to depoling. Here, conformable shear mode ultrasonic transducers are designed and made of flexible piezoelectric poly (L‐lactic acid) (PLLA) fibers on both flat and tubular structures. The electromechanical responses over a macroscopic area of the transducers are evaluated in a wide frequency range up to 500 kHz. The PLLA fiber‐based shear mode ultrasonic transducers exhibit a consistent sensitivity of detecting defects in liquid and air. In addition, the only shear mode in PLLA fibers originates from crystal structure without requiring electrical poling to render piezoelectricity, thus does not depole due to aging. The theoretical analyses including ab initio calculations and experimental results on both flat and tubular structures show the great potential of PLLA material and significant advantage of PLLA fiber‐based shear mode ultrasonic transducers for underwater SHM applications. [ABSTRACT FROM AUTHOR]

PLDxL copolymers were synthesized from physically stable rigid poly(l‐lactic acid) (PLLA) and a few different molecular weights of polydimethylsiloxane (PDMS) to increase the O2 and CO2 permeabilities of PLLA films and make them acceptable for packaging highly respirable products. The effect of PDMS on the morphology, mechanical properties, and gas permeability of PLDxL was investigated. Copolymers showed approximately 10 times the fracture strain and 1.7 times the CO2 and O2 permeabilities of neat PLLA. Additionally, PLDxL maintained an increased CO2/O2 perm‐selectivity consistent between 5 and 40°C. Passive modified atmosphere packaging of Brassica chinensis L was developed to assess the membrane's impact on headspace gas inside the package. The results showed that poly(amide)/poly(ethylene) packaging with 48 cm2 PLD1.8L membrane as a breathing window can provide 50 g B. chinensis L. with a healthy atmosphere of 3%–8% O2 and 5%–8% CO2 between 6 and 22 days. Vegetables packaged in PLD1.8L had the lower respiration rate, lower nitrite contents, and less proliferation of microorganisms. Moreover, a suitable atmosphere kept vegetables with higher ascorbic acid and a good appearance after more than 2 weeks of storage at 5°C. Practical Application: The permeability of the PLLA‐based membrane can be adjusted for the breathable window membrane of sealed fresh products. In the future, several types of film could be developed to match the respiratory and metabolic characteristics of different kinds of products. Such PLLA‐based specialized membranes can refine the fresh‐keeping function and be more attractive to the customer. [ABSTRACT FROM AUTHOR]

Objective: The primary objective of this research was to develop a poly(l‐lactic acid) (PLLA) scaffold and evaluate critical characteristics essential for its biologic use as a craniofacial implant. Materials and Methods: PLLA scaffolds were designed and fabricated using fused deposition modeling technology. The surface morphology and microarchitecture were analyzed using scanning electron microscopy (SEM) and microCT, respectively. Crystallography, compressive modulus, and the piezoelectric potential generated upon mechanical distortion were characterized. Hydrolytic degradation was studied. MG63 osteoblast‐like cell proliferation and morphology were assessed. Results: The porosity of the scaffolds was 73%, with an average pore size of 450 µm and an average scaffold fiber thickness of 130 µm. The average compressive modulus was 244 MPa, and the scaffolds generated an electric potential of 25 mV upon cyclic/repeated loading. The crystallinity reduced from 27.5% to 13.9% during the 3D printing process. The hydrolytic degradation was minimal during a 12‐week period. Osteoblast‐like cells did not attach to the uncoated scaffold but attached well after coating the scaffold with fibrinogen. They then proliferated to cover the complete scaffold by Day 14. Conclusion: The PLLA scaffolds were designed and printed, proving the feasibility of 3D printing as a method of fabricating PLLA scaffolds. The elastic modulus was comparable to that of trabecular bone, and the piezoelectric properties of the PLLA were retained after 3D printing. The scaffolds were cytocompatible. These 3D‐printed PLLA scaffolds showed promising properties akin to the natural bone, and they warrant further investigation for bone regeneration. [ABSTRACT FROM AUTHOR]

Background: Electrospun fibers are widely studied in regenerative medicine for their ability to mimic the extracellular matrix (ECM) and provide mechanical support. In vitro studies indicated that cell adhesion and migration is superior on smooth poly(L-lactic acid) (PLLA) electrospun scaffolds and porous scaffolds once biofunctionalized with collagen. Methods: The in vivo performance of PLLA scaffolds with modified topology and collagen biofunctionalization in full-thickness mouse wounds was assessed by cellular infiltration, wound closure and re-epithelialization and ECM deposition. Results: Early indications suggested unmodified, smooth PLLA scaffolds perform poorly, with limited cellular infiltration and matrix deposition around the scaffold, the largest wound area, a significantly larger panniculus gape, and lowest re-epithelialization; however, by day 14, no significant differences were observed. Collagen biofunctionalization may improve healing, as collagen-functionalized smooth scaffolds were smallest overall, and collagen-functionalized porous scaffolds were smaller than non-functionalized porous scaffolds; the highest re-epithelialization was observed in wounds treated with collagen-functionalized scaffolds. Conclusion: Our results suggest that limited incorporation of smooth PLLA scaffolds into the healing wound occurs, and that altering surface topology, particularly by utilizing collagen biofunctionalization, may improve healing. The differing performance of the unmodified scaffolds in the in vitro versus in vivo studies demonstrates the importance of preclinical testing. [ABSTRACT FROM AUTHOR]

The toughened poly(L-lactic acid)/poly(butylene succinate-butylene terephthalate) (PLLA/PBST) blend with enhanced melt strength and excellent low temperature toughness and strength was prepared by melt compounding through in situ compatibilization reaction in presence of multifunctional epoxy compound (ADR). The PLLA/PBST blend was an immiscible system, and the compatibility of the PLLA/PBST blend was improved after adding ADR. FTIR and GPC curves confirmed the formation of the PLLA-g-PBST copolymer, which improved the interfacial bonding of the blend and therefore the PLLA/PBST/ADR blend showed excellent melt strength and mechanical properties. For the PLLA/PBST/ADR blend with 70/30 PLLA/PBST content, the complex viscosity increased significantly with increasing ADR content. Moreover, the tensile strength, elongation at break and impact strength all increased obviously with increasing the ADR content. The elongation at break of the blend reached the maximum value of 392.7%, which was 93.2 times that of neat PLLA. And the impact strength of the blend reached the maximum value of 74.7 kJ/m2, which was 21.3 times that of neat PLLA. Interestingly, the PLLA/PBST/ADR blend exhibited excellent low-temperature toughness and strength. At −20 °C, the elongation at break of the PLLA/PBST/ADR blend was as high as 93.2%, and the impact strength reached 18.8 kJ/m2. Meanwhile, the tensile strength of the blend at low temperature was also high (64.7 MPa), which was beneficial to the application of PLA in the low temperature field. In addition, the PLLA/PBST/ADR blend maintaind good biodegradability, which was of great significance to the wide application of PLLA. [ABSTRACT FROM AUTHOR]

In this work, PLLA and CD/PLLA nanofibers were fabricated using electrospinning and utilized as a particulate matter (PM) and volatile organic compounds (VOCs) filter. The electrospun PLLA and CD/PLLA were characterized with various techniques, including SEM, BET, FTIR, XRD, XPS, WCA, DSC, tensile strength testing, PM and VOCs removal efficiency, and triboelectric performance. The results demonstrated that the best air filter was 2.5 wt%CD/PLLA, which performed the highest filtration efficiencies of 96.84 ± 1.51% and 99.38 ± 0.43% for capturing PM2.5 and PM10, respectively. Its PM2.5 removal efficiency was 16% higher than that of pure PLLA, which were contributed by their higher surface area and porosity. These 2.5 wt%CD/PLLA nanofibers also exhibited the highest and the fastest VOC entrapment. For triboelectric outputs, the 2.5 wt%CD/PLLA-based triboelectric nanogenerator provided the highest electrical outputs as 245 V and 84.70 μA. These give rise to a three-fold enhancement of electrical outputs. These results indicated that the 2.5 wt%CD/PLLA can improve surface charge density that could capture more PM via electrostatic interaction under surrounding vibration. Therefore, this study suggested that 2.5 wt%CD/PLLA is a good candidate for a multifunction nanofibrous air filter that offers efficient PM and VOC removal. [ABSTRACT FROM AUTHOR]

The use of biodegradable materials such as cellulose and polyesters can be extended through the combination, as well as modification, of these biopolymers. By controlling the molecular structure and composition of copolymers of these components, it should also be possible to tailor their material properties. We hereby report on the synthesis and characterization of cellulose-based graft copolymers with a precise molecular composition and copolymer architecture. To prepare such materials, we initially modified cellulose through the regioselective protection of the 6-OH group using trityl chloride. The 6-O protected compound was then alkylated, and deprotection at the 6-OH group provided the desired 2,3-di-O-alkyl cellulose compounds that were used as macroinitiators for ring opening polymerization. Regioselective modification was hereby necessary to obtain compounds with an exact molecular composition. Ring opening polymerization, catalyzed by Sn(Oct)2, at the primary 6-OH group of the cellulose macroinitiator, using L-lactide or ε-caprolactone, resulted in graft copolymers with the desired functionalization pattern. The materials were characterized using Fourier-transform infrared spectroscopy, 1H- and 13C- nuclear magnetic resonance spectroscopy, size exclusion chromatography as well as X-ray diffraction, and differential scanning calorimetry. PCL-based copolymers exhibited distinct melting point as well as a crystalline phase of up to 47%, while copolymers with PLA segments were highly amorphous, showing a broad amorphous reflex in the XRD spectra, and no melting or crystallization points were discernible using differential scanning calorimetry. [ABSTRACT FROM AUTHOR]

Adding nucleating agents has been a successful strategy to boost the heat resistance of poly(L-lactic acid) (PLLA) by increasing the crystallinity. In this study, a new series of bio-based complexes as nucleating agents for PLLA, including twelve combinations of three eco-friendly metal ions (Zn, Mg, Ca) and four biomass-derived α-hydroxy acids, were successfully synthesized to respectively investigate the effects of metal ions as well as ligands on nucleation capacity of complexes. By investigating the non-isothermal and isothermal crystallization at 135 °C of PLLA with 0.3 wt% loading of complexes, both zinc and magnesium salts of L-mandelic acid showed excellent nucleation capacities. And magnesium L-mandelate performed better, raising the crystallinity of PLLA to 44.4 % as well as minimizing its crystallization half-time from 73 min to 2.7 min. The growth and denser distribution of PLLA spherulites on the salt surface were also observed by POM, reflecting epitaxial nucleation as the possible mechanism. A novel inspiration, utilizing VESTA software to simulate the crystal structure of zinc L-mandelate (Zn(L-MA) 2), was proposed to determine the nucleation mechanism. Also, using polyethylene terephthalate (PET) as a test protocol, the rationality of the model could be approved by checking the fitness of nucleating prediction and experiment results. [Display omitted] • Biomass-derived ligands and non-toxic metal ions synthesized as a class of PLLA efficient nucleating agents. • The nucleation ability and nucleation mechanism of nucleating agents was studied. • A novel strategy using computer simulation was developed to successfully explain the nucleation mechanism. • It has a good nucleation effect on other polyester, such as PET. [ABSTRACT FROM AUTHOR]

In this study, the potential effects of N, N' -dodecanedioic bis(cyclopentanecarboxylic acid) dihydrazide (BCADD) as a new additive in poly(L-lactic acid) (PLLA) was estimated. The comparative study on the melt-crystallization showed that the BCADD as heterogeneous nuclei facilitated crystallization of PLLA in cooling, which indicated by the obvious crystallization exotherms and sharp melt-crystallization peak. Unfortunately, with increasing of BCADD from 0.5 wt% to 3 wt%, it is unexpected that the melt-crystallization peak of the BCADD-nucleated PLLA shifted toward the lower temperature and became flatter, evidencing the importance of BCADD loading for PLLA's crystallization. Additionally, the cooling rate and the final melting temperature were also proved to be important influence factors during PLLA's melt-crystallization process, but in contrast with the effect of the final melting temperature on the melt-crystallization, a higher cooling rate could more seriously weaken crystallization ability of the BCADD-nucleated PLLA. The chemical nucleation mechanism was proposed to explain the promoting effect of BCADD on the crystallization of PLLA via the analysis of frontier orbital energy. The melting behaviors after crystallization further confirmed the crystallization accelerating role of BCADD, and the melting behaviors were affected by the heating rate, crystallization temperature and BCADD loading. Although the onset thermal decomposition of the BCADD-nucleated PLLA occurred at lower temperature comparing with the pure PLLA, the intermolecular interaction of PLLA with BCADD attempted to prevent the decrease of thermal stability. Overall, the addition of BCADD resulted in the complicated effect on the tensile modulus and tensile strength of PLLA, but the elongation at break continuously decreased when increasing BCADD loading. [ABSTRACT FROM AUTHOR]

In the context of today's needs for environmental sustainability, it is important to develop new materials that are based on renewable resources and biodegrade at the end of their life. Bioplastics reinforced by agricultural waste have the potential to cause a revolution in many industrial applications. This paper reports the physical properties and crystallization kinetics of biocomposite films based on poly(L-lactic acid) (PLLA) and 10 wt.% of spent coffee grounds (SCG). To enhance adhesion between the PLLA matrix and SCG particles, a compatibilizing agent based on itaconic anhydride (IA)-grafted PLLA (PLLA-g-IA) was prepared by reactive extrusion using dicumyl peroxide (DCP). Furthermore, due to the intended application of the film in the packaging industry, the organic plasticizer acetyl tributyl citrate (ATBC) is used to improve processing and increase ductility. The crystallization behavior and thermal properties were observed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Crystallinity degree increased from 3,5 (neat PLLA) up to 48% (PLLA/PLLA-g-IA/ATBC/SCG) at the highest cooling rate. The physical properties were evaluated by tensile testing and dynamic mechanical analysis (DMA). The combination of the compatibilizer, SCG, and ATBC led to a synergistic effect that positively influenced the supramolecular structure, internal damping, and overall ductility of the composite films. [ABSTRACT FROM AUTHOR]

BACKGROUND: Poly(L-lactic acid) (PLLA) microparticle (Sculptra®) has been approved by FDA as the dermal filler to regenerate collagen for anti-aging purpose. Because of its irregular particle shape, it is prone to excessive inflammation. OBJECTIVE: To investigate the effects of irradiation on the molecular weight, size and morphology of the poly(L-lactic acid) microspheres, as well as the foreign body reaction and the neocollagenesis stimulation of the poly(L-lactic acid) microspheres dermal filler implanted subcutaneously into back of rabbits. METHODS: Microspheres were prepared by the emulsion-solvent evaporation method and utilized as the dermal filler with the same Sculptra’®s formula. The filler was sterilized by irradiation at 25 and 50 kGy, separately and the molecular weight, size and morphology of the microspheres were analyzed. The MTT assay was used to detect the effects of the microspheres at different concentrations (50, 100, 250, and 500 mg/L calculated by the concentration of microspheres) on the proliferation of mouse fibroblasts. The 25 kGy irradiated dermal filler (experimental group) and saline (control group) were injected into the back of the rabbit subcutaneously. Hematoxylin-eosin staining, Masson staining, and immunofluorescence staining of CD68, type I collagen and type III collagen were performed on the back tissue of the injection site at the set time points. RESULTS AND CONCLUSION: (1) With the increase of the radiation dose, the viscosity, viscosity-average molecular weight and number-average molecular weight of the microspheres decreased significantly, but the irradiation sterilization did not cause significant changes in the particle size and morphology of the microspheres. (2) MTT assay results demonstrated that when the mass concentration of the filler was lower than 250 mg/L, the cell survival rate was all >90%. Even when the material mass concentration reached the highest level 500 mg/L, the cell survival rate was still higher than 80%. Incubation for 72 hours also did not produce significant cytotoxicity. (3) In animal experiments, hematoxylin-eosin staining and CD68 immunofluorescence staining revealed that the filler caused slight inflammatory response from 0.5 to 4 months after implantation, and the inflammatory response reached the highest level at 6 months after implantation. Some microspheres were degraded to irregular shape or with pores on the surface, and the microspheres were degraded completely at 9 months after implantation. (4) In animal experiments, Masson staining and immunofluorescence staining of type I collagen and type III collagen exhibited that at 4 months after implantation, type I collagen was mainly around the microspheres, and type III collagen was mainly at the periphery. At 6 months after implantation, type I collagen near the microspheres increased, and type III collagen at the periphery increased. At 9 months after implantation, the fibrous encapsulation was mainly composed of type I collagen, and the ratio of type I collagen to type III collagen was close to the same at the periphery. (5) The results indicate that injectable poly(L-lactic acid) microsphere filler can stimulate collagen regeneration and can also reduce the degree of inflammatory response. [ABSTRACT FROM AUTHOR]

The transesterification of poly(L-lactic acid) (PLA) with 0.05 M and 0.10 M of tin(II) octoate (Sn(Oct)2), aluminum(III) tri-sec-butoxide (Al(OsBu)3) and titanium(IV) n-butoxide (Ti(OnBu)4) catalysts in CHCl3 was successfully investigated by gel permeation chromatography (GPC) and proton-nuclear magnetic resonance spectroscopy (1H-NMR) techniques. All catalysts were completely and rapidly dissolved in PLA solution. When intramolecular transesterification reaction occurred, the physical appearances of PLA were changed from longer fiber to shorter fiber or power due to the decreasing of molecular weight and chain scission. The transesterification reaction of PLA depended on catalyst concentration, reaction time and catalyst type. From kinetics study, the transesterification of PLA with all catalysts was the first order reaction. The molecular weight of PLA decreased faster at higher catalyst concentration. At identical catalyst concentration, the molecular weight of PLA obtained from transesterification time of 1 d was higher than 2, 3 and 4 d, respectively. The molecular weight of PLA in the presence of Sn(Oct)2 dramatically decreased to 7.33 × 103 g/mol at 4 d when compared with PLA in the absence of Sn(Oct)2 (6.78 × 104 g/mol). From GPC technique, the apparent rate constants of transesterification (kapp) of PLA with 0.10 M of Sn(Oct)2, Ti(OnBu)4 and Al(OsBu)3 were 0.283, 0.085 and 0.073 d−1, respectively. From 1H-NMR technique, the kapp values of PLA with 0.10 M of Sn(Oct)2, Ti(OnBu)4 and Al(OsBu)3 were 0.297, 0.192 and 0.151 d−1, respectively. The lowest apparent half-life (t1/2,app) obtained from the 1H-NMR technique for PLA transesterification with Sn(Oct)2, Ti(OnBu)4 and Al(OsBu)3 was 2.333, 3.610 and 4.589 d, respectively. The transesterification activity of Sn(II), Al(III) and Ti(IV) catalysts for PLA was determined in the following order: Sn(Oct)2 > Ti(OnBu)4 > Al(OsBu)3. From kinetics and mechanistic studies, the transesterification of PLA with these Sn(II), Al(III) and Ti(IV) catalysts was proposed through the intramolecular transesterification. [ABSTRACT FROM AUTHOR]