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1.
Small ; : e2308992, 2024 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-38174631

RESUMO

In this study, lightweight, flexible, and environmentally robust dual-nanofibrous membranes made of carbon nanotube (CNT) and polytetrafluoroethylene (PTFE) are fabricated using a novel shear-induced in situ fibrillation method for electromagnetic interference (EMI) shielding. The unique spiderweb-like network, constructed from fine CNTs and PTFE fibrils, integrates the inherent characteristics of these two materials to achieve high conductivity, superhydrophobicity, and extraordinary chemical resistance. The dual-nanofibrous membranes demonstrate a high EMI shielding effectiveness (SE) of 25.7-42.2 dB at a thickness range of 100-520 µm and the normalized surface-specific SE can reach up to 9931.1 dB·cm2 ·g-1 , while maintaining reliability even under extremely harsh conditions. In addition, distinct electrothermal and photothermal conversion properties can be achieved easily. Under the stimulation of a modest electrical voltage (5 V) and light power density (400 mW·cm-2 ), the surface temperatures of the CNT/PTFE membranes can reach up to 135.1 and 147.8 °C, respectively. Moreover, the CNT/PTFE membranes exhibit swift, stable, and highly efficient thermal conversion capabilities, endowing them with self-heating and de-icing performance. These versatile, flexible, and breathable membranes, coupled with their efficient and facile fabrication process, showcase tremendous application potential in aerospace, the Internet of Things, and the fabrication of wearable electronic equipment for extreme environments.

2.
J Biomed Mater Res A ; 112(6): 825-840, 2024 06.
Artigo em Inglês | MEDLINE | ID: mdl-38158889

RESUMO

Acellular porcine cornea (APC) has been used in corneal transplantation and treatment of the corneal diseases. Sterilization is a key step before the application of graft, and irradiation is one of the most commonly used methods. In this paper, APC was prepared by the physical freeze-thawing combined with biological enzymes, and the effects of the electron beam (E-beam) and cobalt 60 (60Co-γ) at the dose of 15 kGy on the physicochemical properties, structure, immunogenicity, and biocompatibility of the APC were investigated. After decellularization, the residual DNA was 20.86 ± 1.02 ng/mg, and the α-Gal clearance rate was more than 99%. Irradiation, especially the 60Co-γ, reduced the cornea's transmittance, elastic modulus, enzymatic hydrolysis rate, swelling ratio, and cross-linking degree. Meanwhile, the diameter and spacing of the collagen fibers increased. In the rat subcutaneous implantation, many inflammatory cells appeared in the unirradiated APC, while the irradiated had good histocompatibility, but the degradation was faster. The lamellar keratoplasty in rabbits indicated that compared to the E-beam, the 60Co-γ damaged the chemical bond of collagen to a larger extent, reduced the content of GAGs, and prolonged the complete epithelization of the grafts. The corneal edema was more serious within 1 month after the surgery. After 2 months, the thickness of the APC with the two irradiation methods tended to be stable, but that in the 60Co-γ group became thinner. The pathological results showed that the collagen structure was looser and the pores were larger, indicating the 60Co-γ had a more extensive effect on the APC than the E-beam at 15 kGy.


Assuntos
Transplante de Córnea , Elétrons , Suínos , Coelhos , Animais , Ratos , Córnea , Transplante de Córnea/métodos , Esterilização/métodos , Colágeno/análise
3.
Int J Biol Macromol ; 252: 126261, 2023 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-37591438

RESUMO

Plant-derived thermoplastic polyester elastomer (TPEE) is an environment friendly polymer known for its exceptional tear strength and mechanical properties, whose monomers are generated from crops. To prepare high-performance TPEE foams is still challenging due to the intrinsic shrinkage behavior. Herein, two microcellular foaming routes with different charging orders of mixed blowing agents, namely "CO2 firstly charging process (CO2-F-process)" and "N2 firstly charging process (N2-F-process)", were developed to elucidate the effects of mixed blowing agents on foaming behavior. Compared with the case in N2-F-process, more carbon dioxide and less nitrogen were adsorbed in CO2-F-process. Thus, TPEE foams prepared by N2-F-process show less shrinkage and higher creep recovery ratio than those prepared by CO2-F-process. Thanks to better structural stability and smaller shrinkage, TPEE foams prepared by N2-F-process exhibited enhanced strength and resilience. For the foams with similar density, compression strength can be increased by 52 %, and energy loss coefficient can be reduced to 50 %, by using N2-F-process. Thus, not only biomass TPEE foams with enhanced mechanical performance shows promising prospects in those areas that needs lightweight, insulation and high resilience, but also novel microcellular foaming technique with mixed blowing agents opens a new way for developing high-performance polymeric foams.


Assuntos
Elastômeros , Poliésteres , Poliésteres/química , Dióxido de Carbono/química , Polímeros/química
4.
RSC Adv ; 13(23): 15531-15539, 2023 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-37223421

RESUMO

Flexible solar cells, with the merits of structure compactness and shape transformation, are promising power sources for future electronic devices. However, frangible indium tin oxide-based transparent conductive substrates severely limit the flexibility of solar cells. Herein, we develop a flexible transparent conductive substrate of silver nanowires semi-embedded in colorless polyimide (denoted as AgNWs/cPI) via a simple and effective substrate transfer method. A homogeneous and well-connected AgNW conductive network can be constructed through modulating the silver nanowire suspension with citric acid. As a result, the prepared AgNWs/cPI shows low sheet resistance of about 21.3 ohm sq.-1, high transmittance at 550 nm of 94%, and smooth morphology with the peak-to-valley roughness value of 6.5 nm. The perovskite solar cells (PSCs) on AgNWs/cPI exhibit power conversion efficiency of 14.98% with negligible hysteresis. Moreover, the fabricated PSCs maintain nearly 90% initial efficiency after bending for 2000 cycles. This study sheds light on the importance of suspension modification for the distribution and connection of AgNWs and paves a way for the development of high-performance flexible PSCs for practical applications.

5.
J Mech Behav Biomed Mater ; 136: 105494, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-36209588

RESUMO

The current clinical treatments for complications caused by hepatobiliary surgery still have some inevitable weaknesses. This study aimed to prepare the acellular porcine common bile duct (APCBD) for repairing biliary defects and damage. The porcine common bile duct was decellularized by the freeze-thaw method combined with nuclease treatment, and the efficacy of acellularization was confirmed by the DNA quantification and histological structure. The results showed that the residual DNA content was reduced from 854.67 ± 9.71 ng/mg to 5.43 ± 0.85 ng/mg, and the natural structure and shape of the bile duct were well preserved. The biomechanical properties such as the tensile strength, elastic modulus, and elongation-at-break of the APCBD in the transverse and longitudinal direction indicated that the APCBD meets the requirements of the biomechanical strength in replacement. In addition, the results of the immunotoxicity test showed there was no significant difference in the body weights, organ coefficient, hematology, and immune histology between the experimental groups (three subgroups) and the negative control group, which demonstrated the prepared APCBD had no obvious toxicity to the immune system in vivo and might be a suitable biomaterial for the bile duct repairing.


Assuntos
Ductos Biliares , Ducto Colédoco , Suínos , Animais , Ducto Colédoco/cirurgia , Materiais Biocompatíveis , Módulo de Elasticidade , DNA
6.
Biomater Adv ; 137: 212822, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35929237

RESUMO

The Boston Keratoprosthesis type I (B-KPro) is widely used in the world, but the lack of donor corneas limits its application. This study aims to prepare the acellular porcine cornea (APC) crosslinked with ultraviolet A (UVA)/riboflavin instead of donor corneas as the scaffold for B-KPro. Decellularization of freeze-thaw combined with biological enzymes resulted in approximately 5 ng/mg DNA residue, the a-Gal removal rate of 99%, and glycosaminoglycans retention at a high level of 46.66 ± 2.59 mg/mg. UVA/ riboflavin cross-linking was adopted to induce the formation of new chemical bonds between adjacent collagen chains in the corneal stroma to improve the mechanical properties and resistance to enzymatic hydrolysis. Through comprehensive analysis of the biomechanics, enzyme degradation, immunogenicity and histological structure of the APC crosslinked at different times, CL3 (irradiation conditions, 365 nm, 3 mW/cm, 80 min, both sides) was selected and transplanted into the rabbit cornea model through interlamellar keratoplasty and penetrating keratoplasty as the scaffold of the B-KPro. Compared with the native porcine cornea (NPC) and APC, the experiment of interlamellar pocket indicated that the structure of CL3 was homogeneous without degradation and vascularization in vivo at 12 weeks after surgery. Simultaneously, the results of transplantation of B-KPro showed complete epithelialization of CL3 within 1 week, and neovascularization of the cornea indicated rejection but could be controlled with immunosuppressants. At 3 months postoperatively, the lens of B-KPro remained transparent, and the structure of CL3 was compact and uniform, accompanied by the migration and proliferation of a large number of stromal cells without degradation, suggesting the CL3 could be a promising corneal substitute.


Assuntos
Córnea , Doenças da Córnea , Animais , Córnea/cirurgia , Doenças da Córnea/metabolismo , Reagentes de Ligações Cruzadas/metabolismo , Fármacos Fotossensibilizantes/metabolismo , Próteses e Implantes , Coelhos , Riboflavina/farmacologia , Suínos , Raios Ultravioleta
7.
Molecules ; 27(14)2022 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-35889309

RESUMO

Polysaccharides were extracted from natural sources with various biological activities, which are strongly influenced by their chemical structure and molecular weight. In this research, mannans polysaccharides were obtained from Saccharomyces cerevisiae by ethanol precipitation. The molecular weight of YM50, YM70, and YM90 mannans was 172.90 kDa, 87.09 kDa, and 54.05 kDa, respectively. Scanning electron microscopy of YM 90 mannans showed a rough surface with numerous cavities, while the surfaces of YM50 and YM70 were relatively smooth. Sepharose CL-6B and FTIR indicated that mannans had the characteristic bands of polysaccharides. The antioxidant activities of polysaccharides were evaluated in vitro using various assays. Mannans showed a good scavenging activity of DPPH radicals which depend on the molecular weight and concentration, and a higher scavenging activity of hydroxyl radical than ferric-reducing power activities. For the three types of mannans, cytotoxicity and hemolytic activity were rarely detected in mice erythrocytes and Caco-2 cells. Those results could contribute to the further application of mannans from Saccharomyces cerevisiae in the food and medicine industry.


Assuntos
Antioxidantes , Mananas , Animais , Antioxidantes/química , Antioxidantes/farmacologia , Células CACO-2 , Humanos , Mananas/química , Mananas/farmacologia , Camundongos , Peso Molecular , Polissacarídeos/química , Saccharomyces cerevisiae
8.
STAR Protoc ; 3(3): 101585, 2022 09 16.
Artigo em Inglês | MEDLINE | ID: mdl-35880129

RESUMO

This protocol details the steps for preparation of a recently developed bioink, named YM-MA, which is based on methacrylate anhydride-modified yeast mannan. A light-assisted 3D bioprinting is performed to analyze the printability of YM-MA bioink. We describe how cell experiments, animal models of subcutaneous implantation in a Sprague Dawley rat model, and nude mice are used to evaluate the cytocompatibility, histocompatibility, and chondrogenesis of YM-MA bioink. This protocol provides a versatile strategy to develop bioinks of polysaccharides with chemical modification sites such as hydroxyl group. For complete details on the use and execution of this protocol, please refer to Huang et al. (2021).


Assuntos
Bioimpressão , Animais , Bioimpressão/métodos , Mananas , Camundongos , Camundongos Nus , Impressão Tridimensional , Ratos , Ratos Sprague-Dawley , Engenharia Tecidual/métodos , Alicerces Teciduais
9.
Int J Biol Macromol ; 215: 57-66, 2022 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-35718146

RESUMO

High-performance microcellular polymer foams have been widely used all over the world, while the excessive usage of petroleum-based polymers caused serious environmental problems. As the eco-friendly awareness is increasing significantly, poly (L-lactic acid) (PLLA), as a typical biomass polymer, has gradually attracted widespread attention. However, the slow crystallization and poor melt strength of PLLA lead to low foaming ability and thus limiting its industrial applications. Herein, a novel and scalable strategy by coupling in-situ fibrillation and mold-opening microcellular injection molding (MOMIM) was developed to fabricate lightweight and tough PLLA/polytetrafluoroethylene (PTFE) foams. Thanks to the reticulated in-situ PTFE nanofibrils with a diameter of 100-200 nm, the crystallization and viscoelasticity of PLLA were dramatically promoted, and further contributing to its foaming ability. The expansion ratio of the MOMIM PLLA/PTFE foam was increased by 86 % compared with the regular microcellular injection molded (RMIM) PLLA foam. Moreover, the lower foam density and the toughening effect of PTFE nanofibrils resulted in the outstanding ductility of the PLLA/PTFE foams, whose tensile elongation, flexural strength, and impact strength were maximally increased by 52 %, 28 %, and 48 %, compared with PLLA foams. More importantly, the thermally-insulating performance and surface quality of PLLA/PTFE foams were also greatly improved.


Assuntos
Nanocompostos , Politetrafluoretileno , Cristalização , Ácido Láctico/química , Poliésteres/química , Polímeros/química
10.
FEMS Microbiol Lett ; 368(21-24)2022 01 25.
Artigo em Inglês | MEDLINE | ID: mdl-34875071

RESUMO

CoQ10, which has been widely applied in medicine by dietary supplement, possesses important functions in antioxidant process and bioenergy generation. Iterative mutagenesis introduced by atmospheric and room temperature plasma (ARTP) treatment was studied to improve the coenzyme Q10 (CoQ10) production of Rhodobacter sphaeroides (R. sphaeroides), and multiple selection pressures including vitamin K3 (VK3), Na2S and benzoic acid (BA) were adopted for the first time. After two rounds of mutation and screening, a mutant strain R.S 17 was obtained, and the product titer was increased by 80.37%. The CoQ10 titer and cell density reached 236.7 mg L-1 and 57.09 g L-1, respectively, in the fed-batch fermentation, and the CoQ10 content was 22.1% higher than that of the parent strain. In addition, the spectral scanning results indicated the metabolic flux improvement contributing to the CoQ10 production in R.S 17, and the genetic stability was validated. Based on the iterative mutagenesis introduced by ARTP under multiple selection pressures, the promotion of CoQ10 production by R. sphaeroides was achieved. The significant improvement in fermentation performances and the good genetic stability of R.S 17 indicate a potential way for the efficient biosynthesis of CoQ10.


Assuntos
Rhodobacter sphaeroides , Fermentação , Mutagênese , Rhodobacter sphaeroides/genética , Rhodobacter sphaeroides/metabolismo , Temperatura , Ubiquinona/análogos & derivados
11.
Food Funct ; 12(21): 10423-10431, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34596192

RESUMO

Yeast mannans from Saccharomyces cerevisiae (123.2 kDa, 40.5 kDa and 21.3 kDa) were prepared. The scavenging abilities of Fe2+, OH˙, and O2˙- and protective capacities against lipid peroxidation and oxidative DNA damage increased with the reduction of the molecular weights of yeast mannans. The highest scavenging abilities of Fe2+, OH˙ and O2˙- (25.32%, 70.8%, and 61.5%) were observed with YM-90, and it showed an anti-lipid peroxidation capacity of 65.82%, which was much stronger than that of vitamin C (VC), with a thiobarbituric acid-reactive substance (TBARS) inhibition rate of 80.41%. However, the highest DPPH scavenging rate (88.7%) was exhibited by YM-30. In addition, the growth-promoting effect of yeast mannans on Lactobacillus strains was further confirmed, and a 54.2% increment of Lactobacillus plantarum ZWR5 cell viability was achieved by YM-90. The results indicated the potential industrial applications of this yeast mannan technology in therapeutic and nutraceutical production.


Assuntos
Antioxidantes/metabolismo , Lactobacillus/crescimento & desenvolvimento , Lactobacillus/metabolismo , Mananas/metabolismo , Saccharomyces cerevisiae/metabolismo , Sequestradores de Radicais Livres/metabolismo , Peroxidação de Lipídeos/efeitos dos fármacos , Peso Molecular , Estresse Oxidativo/efeitos dos fármacos
12.
Polymers (Basel) ; 13(19)2021 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-34641096

RESUMO

Poly(l-lactic acid) (PLLA) crystal possesses a complex polymorphism, and the formation mechanism of various crystal forms has been a hot research topic in the field of polymer condensate matter. In this research, five kinds of PLLA with different molecular weights were prepared by ring-opening polymerization with strict dehydration operations and multistep purification treatments. Then, thin film isothermal crystallization experiments were carried out to obtain crystallized samples. Previous research has proven that the PLLA α crystal form is usually formed at a temperature above 120 °C and the PLLA δ (or α') crystal form is usually formed at a temperature below 120 °C. However, in this research, the characterization results indicated that the PLLA crystal changed from δ form to α form with the decrease of molecular weight at a temperature of 80 °C. Considering the molecular weight effect, the paper argued that the transitions of the α/δ crystal form are not only associated with temperature, but also related to entanglement state before crystallization. The small-angle X-ray scattering of the PLLA crystal and rheology analysis of the PLLA melt before crystallization further proved the significant role of entanglement. Finally, we tentatively proposed the entanglement effect mechanism on the transitions of the α/δ crystal form.

13.
Biomed Mater ; 16(5)2021 08 19.
Artigo em Inglês | MEDLINE | ID: mdl-34348252

RESUMO

3D bioprinting technology displays many advantages for tissue engineering applications, but its utilization is limited by veryfew bioinks available for biofabrication. In this study, a novel type of bioink, which includes three methacryloyl modifiedmannans, was introduced to 3D bioprinting for tissue engineering applications. Yeast mannan (YM) was modified by reactingwith methacrylate anhydride (MA) at different concentrations, and three YM derived bioinks were obtained, which weretermed as YM-MA-1, YM-MA-2 and YM-MA-3 and were distinguished with different adjusted methacrylation degrees. TheYM derived bioink displayed an advantage that the mechanical properties of its photo-cured hydrogels can be enhanced withits methacrylation degree. Hence, YM derived bioinks are fitted for the mechanical requirements of most soft tissueengineering, including cartilage tissue engineering. By selecting chondrocytes as the testing cells, well cytocompatibility of YM-MA-1, YM-MA-2 had been confirmed by CCK-8 method. Following photo-crosslinking and implantation into SD rats for 4 weeks, thein vivobiocompatibility of the YM-MA-2 hydrogel is acceptable for tissue engineering applications. Hence, YM-MA-2 was chosen for 3D bioprinting. Our data demonstrated that hydrogel products with designed shape and living chondrocytes have been printed by applying YM-MA-2 as the bioink carrying chondrocytes. After the YM-MA-2 hydrogel with encapsulated chondrocytes was implanted subcutaneously in nude mice for 2 weeks, GAG and COLII secretion was confirmed by histological staining in YM-MA-2-H, indicating that the YM derived bioink can be potentially applied to tissue engineering by employing a 3D printer of stereolithography.


Assuntos
Materiais Biocompatíveis , Bioimpressão/métodos , Mananas , Engenharia Tecidual/métodos , Animais , Materiais Biocompatíveis/química , Materiais Biocompatíveis/farmacologia , Células Cultivadas , Condrócitos/citologia , Condrócitos/efeitos dos fármacos , Hidrogéis/química , Hidrogéis/farmacologia , Masculino , Mananas/química , Mananas/farmacologia , Camundongos , Camundongos Nus , Impressão Tridimensional , Coelhos
14.
RSC Adv ; 11(9): 5284-5290, 2021 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-35424459

RESUMO

A complete and efficient utilization of sweet sorghum stalk including sweet sorghum juice (SSJ) and sweet sorghum bagasse (SSB) was achieved via the open simultaneous saccharification and fermentation (SSF) of l-lactic acid. To simplify the pretreatment process and reduce water consumption, a combined hydrolysis approach was applied and the NaOH-pretreated liquor (SL) was utilized as a partial neutralizing agent. In order to further enhance the product titer, the acid hydrolysate of SSJ (SSJAH) was fed, and MgO was used as a neutralizing agent. A product titer of 94 g L-1 was obtained with a productivity of 1.55 g L-1 h-1, and the yield reached 98.31%. Totally, 274.79 g l-lactic acid was produced from 1 kg sweet sorghum stalk, and 83.22% water was saved compared with the previous study based on alkali pretreatment of SSB. This study provides an effective process for l-lactic acid biosynthesis from lignocellulosic substrates.

15.
ACS Nano ; 14(10): 14057-14069, 2020 Oct 27.
Artigo em Inglês | MEDLINE | ID: mdl-32926610

RESUMO

A hard carbon material with free-standing porous structure and high contents of heteroatom functional groups is considered to be a potential anode for potassium-ion batteries (PIBs). Herein, a free-standing phosphorus/nitrogen cofunctionalized porous carbon monolith (denoted as PN-PCM) anode for PIBs is successfully fabricated via a supercritical CO2 foaming technology, followed by amidoximation, phosphorylation, and thermal treatment. Thanks to the synergistic effect of a three-dimensional macroporous open structure and high P/N contents of 6.19/5.74 at%, the PN-PCM anode delivers an excellent reversible specific capacity (396 mA h g-1 at 0.1 A g-1 after 300 cycles) with high initial Coulombic efficiency (63.6%), a great rate performance (168 mA h g-1 at 5 A g-1), and an ultralong cycling stability (218 mA h g-1 at 1 A g-1 after 3000 cycles). Theoretical calculations clarify that in a P/N cofunctionalized carbon, the P-C bonds devote more to enhancing the potassium storage via adsorption and improving electronic conductivity of carbon, while P-O bonds contribute more to enlarging the interlayer distance of carbon and reducing the ion diffusion barrier.

16.
J Biomed Mater Res B Appl Biomater ; 108(7): 2754-2764, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32154984

RESUMO

Current poly-l-lactide acid (PLLA) scaffolds have issues of inadequate mechanical strength leading to thrombosis formation. Designing a novel bioabsorbable PLLA stent with a novel structure and improved mechanical property is urgently needed. In this study, stent structure modification and optimization based on bioresorbable vascular scaffold Version 1.1 (BVS 1.1, Abbott Laboratories) were conducted. The mechanical property of the redesigned stent was studied using both computerized finite element analysis and experimental mechanical deformation testing, including radial strength (RS), acute recoil (AR), foreshortening (FS), and bending stiffness (BS). The simulated and experimental results showed that the mechanical properties of the modified structure were significantly improved (modified stent vs. BVS 1.1: RS: 2.25 vs. 1.29 N/mm; AR: 3.03 vs. 4.41%; FS: 1.13 vs. 6.89%; BS: 1.49 vs. 0.72 N mm2 ).


Assuntos
Vasos Coronários , Poliésteres/química , Desenho de Prótese , Stents , Análise de Elementos Finitos , Humanos
17.
Int J Biol Macromol ; 138: 144-155, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31306706

RESUMO

Environmental friendly and non-toxic polylactic acid (PLA) foam exhibits a promising perspective in many areas. However, PLA shows very poor foaming ability. Herein, silane-modified glass fiber (GF) was compounded with PLA to improve its foaming ability. Thanks to the increased melt viscoelasticity and melt strength, and the enhanced crystallization by adding GF, PLA/GF composites show dramatically improved foaming ability, characterized by widened processing window, increased expansion ratio, and improved cellular uniformity. Compared with pure PLA foam, PLA/GF composite foam shows dramatically enhanced mechanical properties in compressive strength and modulus. For foams with the same expansion ratio of 20-fold, the incorporation of 10 wt% GF led to increased compressive strength and modulus by 44.8% and 92.0%, respectively. The PLA/GF composite foam with an expansion ratio of 24.2-fold has a low thermal conductivity of 31.4 mW/m·K, which is comparable with the excellent thermal insulation performance of commercial polymer foams.


Assuntos
Dióxido de Carbono/química , Vidro/química , Poliésteres/química , Temperatura , Fenômenos Mecânicos , Reologia
18.
Soft Matter ; 15(28): 5714-5727, 2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-31265051

RESUMO

Since CO2 is a kind of nontoxic, non-flammable and biocompatible fluid, introducing CO2 in the PLLA formation process has been regarded as a green way to the manufacture of biological products or medical supplies. However, it is still a challenge to understand the influence of CO2 on the crystal growth behavior of PLLA. Here, we developed an in situ high-pressure observation system, composed of optics, polarization optics and a small angle laser scattering system, to record the growth process of PLLA crystals in a pressurized CO2 environment. It is found that, at a low temperature (near Tg), low pressure CO2 (0.5 MPa in this work) can still induce the formation of numerous micron-sized spherulites of PLLA. Therefore, the introduction of CO2 can significantly enhance the crystallization ability of PLLA and decrease the crystallization temperature, which is helpful in improving the mechanical properties of PLLA products. We also found that a snowflake-shaped crystal was assembled by rhombic lamellae under pressurized CO2. There is a melt accumulation zone surrounding the growth front of the snowflake-shaped crystal, indicating that the growth front nucleation is limited by the pressurized CO2. This melt accumulation zone is quite different from the melt depletion zone existing ahead of the reported dendritic crystal front. Interestingly, in a high-pressure CO2 environment, a kind of bamboo-like branch is formed in a rhythmic growth mode. The repeating unit of the bamboo-like branch is constructed by an asymmetric terrace crystal originated from screw dislocation in the melt accumulation zone. These results demonstrated that CO2 has a remarkable tunability on the polymer crystal morphology.

19.
J Colloid Interface Sci ; 542: 233-242, 2019 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-30763890

RESUMO

The preparation of high-expansion open-cell foam for oil spill clean-ups is important, but still challenging with linear isotactic polypropylene (PP). Therefore, a cooling batch foaming method was designed to fabricate the high-expansion PP foams using supercritical CO2 as a blowing agent. To investigate the relation between the crystallization and foaming of PP, an in-situ visualization system was employed. It is found that the CO2 dissolved in polymer melt depresses the crystallization temperature and nucleation of PP. When the foaming is triggered before the crystallization, high-expansion foams can be prepared. Moreover, foaming occurring before crystallization helps to produce an open-cell structure owing to a structural inhomogeneity induced by the PP crystallization. According to the hydrophobicity and oil absorption capacity tests, the open-cell foam prepared at 20 MPa and 135 °C exhibits a large water contact angle of 151.5° and a high adsorption capacity of 48.9 g/g for carbon tetrachloride. Further, it exhibits an excellent reusability for oil recovery in the cyclic adsorption and squeezing process. Therefore, the fabricated high-expansion open-cell foam shows good application prospects in oil spill clean-up fields.

20.
ACS Appl Mater Interfaces ; 11(9): 9125-9135, 2019 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-30741523

RESUMO

Sodium-ion batteries (SIBs), a promising candidate for large-scale energy storage systems, have recently attracted significant attention because of the low cost and high availability of the sodium resource. Hard carbon with a free-standing structure and plenty of active sites is considered to be the most potential anode material for SIBs. However, keeping a balance between the excellent performance and low cost for the large-scale commercial production of carbon anodes is still a great difficulty. Herein, a free-standing nitrogen-doped 3D hierarchically porous carbon monolith (denoted as 3DHPCM) anode for SIBs is successfully fabricated via a novel supercritical CO2 foaming technology and thermal treatment. Thanks to the tunable macro-meso-microporous and disordered structures, the 3DHPCM exhibits a high reversible specific capacity (281 mA h g-1 after 300 cycles at 50 mA g-1), superior rate performance (67 mA h g-1 at 10 A g-1), and excellent long-term cycling stability (175 mA h g-1 after 3000 cycles at 500 mA g-1). Remarkably, the 3DHPCM with such a high performance is fabricated via an environmentally friendly strategy from low-cost polyacrylonitrile and polymethyl methacrylate. Therefore, the strategy has great potential in practical application for fabricating high-performance hard carbon anodes and other composite electrodes for SIBs and more energy storage devices.

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