公斤级生物基聚对苯二甲酸丙二醇酯制备及性能

以对苯二甲酸、生物基1,3-丙二醇为原料,选用钛酸四丁酯为催化剂,通过熔融缩聚工艺在5 L不锈钢反应釜中制备了公斤级生物基聚对苯二甲酸丙二醇酯(PTT)。研究了不同相对分子质量对生物基PTT性能的影响。采用核磁共振对所合成的PTT结构进行分析表征,采用乌氏黏度计测试聚酯特性黏度,换算得到聚酯黏均分子量在(4.7~6.3)×10^(4)之间。采用差示扫描量热法、X射线衍射仪和偏光显微镜研究了相对分子质量对结晶熔融行为的影响,结果表明,结晶度和结晶速率随着相对分子质量增加而减小,平衡熔点则随着相对分子质量的增加而升高,但均在相对分子质量高于5.5×10^(4)达到平衡;流变测试表明,相对分子质量的增加提高了材料的弹性,降低了黏性;力学性能测试表明,所有样品在单轴拉伸时均出现二次屈服现象,屈服强度随着相对分子质量的增加而增大,断裂伸长率则先增大后减小。该研究对获得具有实用价值的高性能生物基PTT聚酯具有重要意义。

悬浇变截面混凝土连续箱浇施工线形控制分析

本文以某大桥为工程依托,箱梁采用悬臂浇筑法施工,分1#~7#块对梁段,即5m×3.5m+2m×4m进行对称悬臂浇筑,通过连续梁桥施工主要是控制桥梁的整体标高和纵向曲线顺滑,平面位置通过锁定可以有效的控制,竖向挠度控制的好坏直接影响到连续梁桥成桥后投入使用后下的线形变化。因此,预应力混凝土连续梁桥施工控制的原则是主要控制主梁的设计达标程度和线形平稳性,其次是保证不同梁段产生的应力在设计和质量要求范围内。该大桥施工现场的线性监控中,一般悬臂施工过程中节段梁段都是静定状态,合拢中不另行增加重量,成桥过后内形状都是处在偏离设计值差距,为以后同类桥梁的施工提供参考与借鉴。

Phonon dispersion relations of crystalline solids based on LAMMPS package

The phonon dispersion relations of crystalline solids play an important role in determining the mechanical and thermal properties of materials.The phonon dispersion relation,as well as the vibrational density of states,is also often used as an indicator of variation of lattice thermal conductivity with the external stress,defects,etc.In this study,a simple and fast tool is proposed to acquire the phonon dispersion relation of crystalline solids based on the LAMMPS package.The theoretical details for the calculation of the phonon dispersion relation are derived mathematically and the computational flow chart is present.The tool is first used to calculate the phonon dispersion relation of graphene with two atoms in the unit cell.Then,the phonon dispersions corresponding to several potentials or force fields,which are commonly used in the LAMMPS package to modeling the graphene,are obtained to compare with that from the DFT calculation.They are further extended to evaluate the accuracy of the used potentials before the molecular dynamics simulation.The tool is also used to calculate the phonon dispersion relation of superlattice structures that contains more than one hundred of atoms in the unit cell,which predicts the phonon band gaps along the cross-plane direction.Since the phonon dispersion relation plays an important role in the physical properties of condensed matter,the proposed tool for the calculation of the phonon dispersion relation is of great significance for predicting and explaining the mechanical and thermal properties of crystalline solids.

Redox-responsive phenyl-functionalized polylactide micelles for enhancing Ru complexes delivery and phototherapy

Poly(ethylene glycol)-poly(lactic acid)block copolymer(PEG-PLA)is one of the most widely used biomedical polymers in clinical drug delivery owing to its biocompatibility and biodegradability.However,endowing PEG-PLA micelles with high drug loading,self-assembly stability and fast intracellular drug release is still challenging.Redox-responsive diblock copolymers(MPEG-SS-PMLA)of poly(ethylene glycol)and phenyl-functionalized poly(lactic acid)with disulfide bond as the linker are synthesized to prepare PLA-based micelles that demonstrate excellent colloidal stability and high Ru loading.Notably,MPEGSS-PMLA achieved a remarkably high Ru loading efficiency of 84.3%due to the existence of strongπ-πstacking between phenyl and Ru complex.MPEG-SS-PMLA exhibited good colloidal stability in physiological condition but quickly destabilized by reductive tumor microenvironment.Interestingly,about 74%of Ru complex was released under 10 mmol/L GSH concentration.Ru-loaded MEPG-SS-PMLA showed efficient delivery and release of Ru complex into MCF-7 cancer cells,achieving enhanced in vitro and in vivo antitumor activity of photodynamic therapy.This feasible functionalization method of MPEG-PLA has appeared to be a clinically viable platform for controlled delivery therapeutic agents and enhanced phototherapy.

Phononic origin of structural lubrication

Atomistic mechanisms of frictional energy dissipation have attracted significant attention.However,the dynamics of phonon excitation and dissipation remain elusive for many friction processes.Through systematic fast Fourier transform(FFT)analyses of the frictional signals as a silicon tip sliding over a graphite surface at different angles and velocities,we experimentally demonstrate that friction mainly excites non-equilibrium phonons at the washboard frequency and its harmonics.Using molecular dynamics(MD)simulations,we further disclose the phononic origin of structural lubrication,i.e.,the drastic reduction of friction force as the contact angle between two commensurate surfaces changes.In commensurate contacting states,friction excites a large amount of phonons at the washboard frequency and many orders of its harmonics that perfectly match each other in the sliding tip and substrate,while for incommensurate cases,only limited phonons are generated at mismatched washboard frequencies and few low order harmonics in the tip and substrate.

Achieving higher performances without an external curing agent in natural magnolol-based epoxy resin

Bio-based epoxy thermoset prepared from renewable biomass raw materials can alleviate fossil energy crisis and reduce environmental pollution,which satisfies the needs of sustainable social development.In this study,a bio-based epoxy thermoset precursor(MGOL-EP) was synthesized from a naturally occurring magnolol through a facile and efficient one-step process.And the fully bio-based epoxy thermoset(MGOL-EP-SC) was obtained by self-curing without adding any other hardener.MGOL-EP-SC revealed an extremely high glass-transition temperature(T_(g)) of 265℃ and char yield of 53.2%(in N;),which were at the highest level among the fully bio-based epoxy thermosets reported so far.In addition,when the MGOL-EP was cured with 4,4’-methylenedianiline(DDM),T_(g)of the MGOL-EP/DDM was decreased by 61℃ and the other comprehensive performance had also been decreased,which was due to a reduction in biphenyl structure content and cross-linking density by adding the external curing agents.Moreover,the MGOL-EP-SC presented certain killing rate(48.4%) to Staphylococcus aureus.These findings provide a new design strategy for engineering high-performance and functional epoxy thermoset with high biomass content.

In-chain functionalization through the combination of ring opening copolymerization and oxime "Click" reaction towards X-ray opaque polylactide copolymers

X-ray imaging functionalization of biodegradable polyesters is a great demand and challenge in biomedical applications.In this work,a strategy of in-chain functionalization through the combination of ring opening copolymerization and oxime "Click" postfunctionalization was developed towards X-ray opaque polylactide copolymers.A functionalized cyclic carbonate was first synthesized and used as comonomer of polylactide copolymers,which were subjected to postfunctionalization of oxime "Click" reaction towards iodinated polylactide copolymers.The chemical structure and physical properties of the target products were traced and confirmed.In vitro cytotoxicity evaluation with 3T3-Swiss albino by Alamar blue demonstrated a low cytotoxicity.The X-ray radiopacity was analyzed by Micro-CT and quantified by Hounsfield Units value,which could be tailorable by the feedstock.It is a promising X-ray visible implantable biomaterial in biomedical applications.

Inherently radiopaque polyurethane beads as potential multifunctional embolic agent in hepatocellular carcinoma therapy

The aim of the current study is to report an inherently radiopaque drug-eluted beads(DEBs)as promising embolic materials for TACE techniques.Firstly,the synthesized radiopaque iodinated polycaprolactonepolyurethanes(I-PCLUs)are synthesized by chain-extending method by using 4,4-′isopropylidinedi-(2,6-diiodophenol)(IBPA)as the radiopacifying agent.Then,doxorubicin(Dox)is introduced as a chemotherapeutic agent into I-PCLU beads via a double emulsification(W/O/W)method.The drug loading and controlled release behavior of two ratios of I-PCLU/Dox are found to be dependent upon the internal porous microstructure,and the radiopacity is well-retained after four weeks drug release.Besides,the I-PCLU/Dox beads exhibit positive in vitro anti-tumor effect.The in vivo intramuscular implantation and liver embolization results demonstrate that I-PCLU beads have good histocompatibility,occlusion effect and X-ray traceability.Furthermore,the drug-loaded I-PCLU beads are performed into a VX2 rabbit hepatocellular carcinoma(HCC)model using a micro-catheter,form embolization of hepatic arteries and inhibit the tumor growth after one week post-injection.Hence,this polymeric system provides a potential radiopaque chemoembolization candidate for HCC and other cancer therapies,which could bring opportunities to the next generation of multifunctional embolic agents.