Biomimetic MXene membranes with negatively thermo-responsive switchable 2D nanochannels for graded molecular sieving

Negatively thermo-responsive 2D membranes,which mimic the stomatal opening/closing of plants,have drawn substantial interest for tunable molecular separation processes.However,these membranes are still restricted significantly on account of low water permeability and poor dynamic tunability of 2D nanochannels under temperature stimulation.Here,we present a biomimetic negatively thermo-responsive MXene membrane by covalently grafting poly(N-isopropylacrylamide)(PNIPAm)onto MXene nanosheets.The uniformly grafted PNIPAm polymer chains can enlarge the interlayer spacings for increasing water permeability while also allowing more tunability of 2D nanochannels for enhancing the capability of gradually separating multiple molecules of different sizes.As expected,the constructed membrane exhibits ultrahigh water permeance of 95.6 L m^(-2) h^(-1) bar^(-1) at 25℃,which is eight-fold higher than the state-of-the-art negatively thermoresponsive 2D membranes.Moreover,the highly temperature-tunable 2D nanochannels enable the constructed membrane to perform excellent graded molecular sieving for dye-and antibiotic-based ternary mixtures.This strategy provides new perspectives in engineering smart 2D membrane and expands the scope of temperature-responsive membranes,showing promising applications in micro/nanofluidics and molecular separation.

Preparation and Thermo-Responsive Properties of Poly(Oligo(Ethylene Glycol)Methacrylate)Copolymers with Hydroxy-Terminated Side Chain

Thermo-responsive random copolymers,poly(2-(2-methoxyethoxy)ethoxyethyl methacrylate-co-(ethylene glycol)methyl ether methacrylate)(P(EO_(2)-co-EO_(4/5)))and poly(2-(2-methoxyethoxy)ethoxyethyl methacrylate-co-ethylene glycol methacrylate(P(EO2-co-EG4/5))are synthesized via atom transfer radical polymerization(ATRP).The successful synthesis and the narrow polydispersity index(PDI)of two copolymers are indicated by 1H nuclear magnetic resonance(1H-NMR)and gel permeation chromatography(GPC)analyses.The transition behaviors of polymers in the aqueous solution are demonstrated by changes in turbidity and particle sizes.The transition behavior of P(EO2-co-EG4/5)is found to be milder than that of P(EO2-co-EO4/5).Moreover,the presence of hydrogen bonds without thermo-responsive properties established by hydroxyl groups in the end-side chain of P(EO_(2)-co-EG_(4/5))hinders the dehydration at the transition temperature(TT).Attenuated total reflection Fourier transform infrared spectrometry(ATR-FTIR)analysis along with contact angle measurements reveals that both P(EO_(2)-co-EO_(4/5))and P(EO_(2)-co-EG_(4/5))films undergo phase transitions from hydrophilicity to hydrophobicity above TT.By examining the swelling and collapse behaviors of the polymer films during phase transitions,it can be concluded that the end hydroxyl groups may establish hydrogen bonds with neighboring ether groups within the films,which remain intact throughout the phase transition process due to their strong bonding interactions.This leads to an increase in steric hindrance within swollen films thereby impeding dehydration processes and inducing hysteresis during phase transitions.

Graft Polymerization of Acryloyloxystarch with Poly (D, L-lactide) Macromonomer——A Potential Drug Delivery Carrier for Oral Administration

Starch is the second largest natural biopolymer. Its unique biodegradable and biocompatible properties make it be increasingly applied to the field of biomedicine. As one kind of polysaccharide, starch is easily degraded into small organic molecules by amylase in the alimentary canal. The fact that the activity of amylase is restrained in the high acid environment in stomach provides an opportunity to prepare an intestinal-specific delivery carrier with

Application of Monodisperse Thermo-Responsive Composite Microgels with Core-Shell Structure Based on Au@Ag Bimetallic Nanorod as Core in Surface Enhanced Raman Spectroscopy Substrate

The monodisperse Au@Ag bimetallic nanorod is encapsulated by crosslinked poly( N-isopropylacrylamide)( PNIPAM) to produce thermo-responsive composite microgel with well-defined core-shell structure( Au@ Ag NR@ PNIPAM microgel)by seed-precipitation polymerization method using butenoic acid modified Au @ Ag NRs as seeds. When the temperature of the aqueous medium increases from 20℃ to 50℃,the localized surface plasmon resonance( LSPR) band of the entrapped Au @ Ag NR is pronouncedly red-shifted because of the decreased spatial distances between them as a result of shrinkage of the microgels,leading to their plasmonic coupling. The temperature tunable plasmonic coupling is demonstrated by temperature dependence of the surface enhanced Raman spectroscopy( SERS) signal of 1-naphthol in aqueous solution. Different from static plasmonic coupling modes from nanostructured assembly or array system of noble metals,the proposed plasmonic coupling can be dynamically controlled by environmental temperature. Therefore, the thermo responsive hybrid microgels have potential applications in mobile LSPR or SERS microsensors for living tissues or cells.

Synthesis of Dendronized Aromatic Polyamides with Chloromethyl Groups in the Periphery by Macromonomer Approach

The preliminary results for one-pot synthesis of dendronized aromatic polyamides with chloromethyl groups in the periphery by approach were reported first time. The GPC analysis of the resulting dendronized polymers has shown typical weight average molecular weight （Mw） of 41554 and a polydispersity of 2.74.

SYNTHESIS AND POLYMERIZATION OF α-METHACRYLYOXYLETHYLOXYCARBONYLMETHYL-ω-(N,N-DIETHYLDITHIOCARBAMYL)POLYSTYRENE MACROMONOMERS

Polystyrene macromonomers with different molecular weight were prepared by radical polymerization of styrene(St) in benzene using β-methacryloxylethyl 2-N,N-diethyldithiocarbamylacetate (MAEDCA) as a monomer-iniferter.Characterization of the macromonomer by ~1H-NMR showed that the end groups were α-methacrylyoxylethyloxycarbonyl-methyl and ω-(N,N-diethyldithiocarbamyl). The macromonomer was difficult to homopolymerize, but it was easilycopolymerized with methyl methacrylate (MMA) initiated by AIBN to form graft copolymers (PMMA-g-PSt) with PStbranches randomly distributed along the PMMA backbone. Copolymerization reaction and the structure of the graft copolymers were strongly affected by M_n and concentration of the macromonomer. The composition and M_n of the purified graft copolymer were determined by ~1H-NMR and GPC analysis.

EFFECTS OF ω-ACRYLOYL POLY (ETHYLENE OXIDE) MACROMONOMER ON EMULSIFIER-FREE EMULSI0N COPOLYMERIZATION OF METHYL METHACRYLATE AND n-BUTYL ACRYLATE

Well-defined nonionic hydrophilic ω-acryloyl poly(ethylene oxide) macro-monomer (PEO-A) has been prepared by living anionic polymerization of ethylene oxidewith diphenyl methyl potassium as the initiator and acryloyl chloride as the reaction termi-nating agent. The polymer was characterized by FTIR and SEC. The emulsifier-free emul-sion polymerization of methyl methacrylate (MMA) and n-butyl acrylate (BA) containingvarious concentrations of PEO-A was studied. In all cases stable emulsion coplymerizationsof MMA and BA were obtained. The stabilizing effect was found to be dependent on themolecular weight and the feed amount of the macromonomer.

Rheological properties of novel thermo-responsive polycarbonates aqueous solutions

Thermo-responsive multiblock polycarbonates were facilely synthesized by covalently binding poly(ethylene glycol)(PEG) and poly(propylene glycol)(PPG) blocks,using triphosgene as coupling agent and pyridine as catalyst.The aqueous solutions of thermo-responsive polycarbonates were investigated by rheological measurements.Steady-state shear measurements reveal that the polycarbonate solutions exhibit shear-thinning behavior and the hydrophilic content has a pronounced effect on the flow behavior of the polycarbonates aqueous solutions.The shear viscosity decreases with increasing poly(ethylene oxide)(PEO) composition.The increase of viscosity with increasing concentration is probably attributed to the formation of stronger network owing to interchain entanglement of PEO block at higher concentration.When the flow curves are fitted to the power law model,flow index is obtained to be less than 1,as exhibiting typical pesudoplastic fluid.The viscoelastic properties of the system also show close dependence on the composition of polycarbonates.Temperature sweep confirms that the multiblock polycarbonates exhibit thermo-responsive properties.For 7% aqueous solution of polycarbonate with composition ratio of EO to PO of 1/1,the sol-gel transition occurs at 37 ℃,which makes the system suitable as an injectable drug delivery system.

The Microstructure and Gelling Mechanism of Thermo-responsive Chitosan Hydrogel System

Thermo-respansive chitosan hydrogel system （TRCHS） was prepared and its mierostructure was investigated by scaning electron microscope （SEM） and mercury intrusion poremaster （MIP）. Based on analyzing the data, a special porosity property was reported at the first time. Its gelling mechanism was studied by a group of contrast experiments. Results may provide experimental and theoretical supports for how to apply it on tissue engineering scaffold and how to influeuee or control its essential properties.

反应条件对PCEs分子结构和分散性的影响及机理

采用水溶液自由基共聚法,将乙二醇单乙烯基聚乙二醇醚与丙烯酸共聚合成了聚羧酸系减水剂(PCEs),深入研究了反应温度、滴加时间和链转移剂用量3个主要因素对PCEs分子结构和分散性的影响及机理.结果表明,反应温度和链转移剂用量对乙二醇单乙烯基聚乙二醇醚的转化率、PCEs的相对分子质量及其分布影响较大,导致PCEs在水泥净浆中的分散性和分散保持性有明显的区别,而滴加时间的影响相对较小.

减水保坍型聚羧酸减水剂的合成及性能研究

以4-羟丁基乙烯基聚氧乙烯醚(VPEG)大单体、丙烯酸(AA)为主要原料,引入保坍单体丙烯酸羟乙酯(HEA),以巯基丙酸(MPA)为链转移剂,在H_(2)O_(2)/L-抗坏血酸(V_(C))氧化还原引发体系下,通过自由基聚合制备出减水保坍型聚羧酸减水剂(V-HEA)。通过红外光谱、凝胶色谱测试对合成的V-HEA进行分子结构表征,并与市售保坍型聚羧酸减水剂(HPWR-S)进行水化热与混凝土性能对比分析。结果表明,V-HEA的最佳合成工艺参数为酸醚比4.4,酯醚比2.5,引发剂、硫酸亚铁和链转移剂掺量分别占大单体质量的0.76%、0.10%和0.74%。掺入硫酸亚铁可提高单体的转化率,且V-HEA的数均分子量为17650,重均分子量为42713,单体转化率高达95.03%。掺入V-HEA时混凝土的水化峰值温度较掺入HPWR-S时延迟4 h 24 min,且第二水化速率峰出现时间延迟约4 h,更加延缓水泥的水化。掺入V-HEA的混凝土2 h坍落度仅损失5.8%,且混凝土强度与掺入HPWR-S产品相当,V-HEA具有较好的应用前景。

Reshaping the imprinting strategy through the thermo-responsive moiety-derived“deep eutectic solvents”effect

As a new concept having emerged in last few years,the“deep eutectic solvents”(DESs)effect integrated into the imprinting technology inevitably exposes design limitations of stimuli-responsive molecularly imprinted polymers(MIPs),as well as inadequate analysis of the adsorption performance of MIPs.Herein,a simple yet defined N-isopropylacrylamide/(3-acrylamidopropyl)trimethylammonium chloride(NIPAM/APTMAC)binary DESs system was proposed to prepare intelligent MIPs with thermo-sensitivity.Accordingly,magnetic and thermo-responsive MIPs based on functional monomers-derived DESs(TMDESs-MIPs1)were synthesized,revealing DESs effect-regulated affinity/kinetics for the enhanced adsorption capability,eco-friendly thermo-regulated elution for high release efficiency,and simple magnetic separation,along with superior selectivity to rhein(RH)and good regeneration ability.TM-DESs-MIPs1 were utilized to extract RH from Cassiae semen samples coupled with high performance liquid chromatography(HPLC),yielding satisfactory recoveries(79.47%−110.82%)and low limits of detection(LOD)(16.67μg/L).Another two kinds of MIPs adopting the thermo-responsive moiety-derived DESs effect strategy further demonstrated great applicability of such intelligent MIPs for analyses of complicated samples.

新型高保坍降黏型聚羧酸减水剂的合成及性能研究

针对目前高强混凝土出现的黏度大及经时坍落度损失大等问题,以新型聚醚类大单体(EPEG)、丙烯酸、丙烯酸羟丙酯及巯基乙醇为主要原料,引入甲基丙烯基山梨醇酯小单体,在常温条件下通过L-抗坏血酸和双氧水氧化还原体系引发自由基聚合反应,通过水溶液聚合方式合成一种新型高保坍降黏型聚羧酸减水剂BT-Z。通过设计正交试验及单因素分析,研究了酸醚比、酯醚比及二元酯用量等因素对其保坍性能及降黏性能的影响,最终得出当酸醚比为3.5∶1,酯醚比为4∶1,二元酯用量为大单体质量的5.5%,链转移剂用量为大单体质量的0.5%时,BT-Z的保坍性能及降黏性能最佳,且具有较好的水泥适应性。

聚醚大单体与聚醚型聚羧酸减水剂的研究进展

聚羧酸减水剂具有减水率高、保坍性好和分子结构可设计性等优点,广泛应用于配制各种混凝土。结合目前研究的聚醚大单体种类和特点,综述了聚醚型聚羧酸减水剂的高温、低温和室温等环境下合成技术的研究进展。

聚(酰胺-co-醚)大分子单体的一步法合成及其接枝共聚

大分子单体法是制备接枝共聚物的重要方法,但是一步法合成结构丰富的杂链大分子单体极具挑战。为此,文章以N-羟乙基丙烯酰胺(HEAA)为单体,通过氧迈克尔加聚反应一步法制备了端双键聚(酰胺-co-醚)大分子单体(PHEAA),并将其与甲基丙烯酸甲酯(MMA)共聚得到接枝共聚物P(HEAA-g-MMA)。用核磁(NMR)、凝胶渗透色谱(GPC)和差示扫描量热仪(DSC)对大分子单体和聚合物的结构和性能进行了表征。结果表明,HEAA可在室温下通过氧迈克尔加聚反应一步生成主链含酰胺和醚键的大分子单体。单体HEAA的转化率接近100%,且不存在乙烯基加成等副反应。将制备的大分子单体与MMA进行自由基共聚,成功得到了接枝共聚物。接枝共聚物分子质量为26700 g/mol,分子质量分布为1.58,其玻璃化转变温度为66.3℃。

国内聚醚大单体的研究现状及展望

近些年,随着现代工程对混凝土性能要求的提高,混凝土外加剂技术及产品研究也在随之进步,其中混凝土外加剂最主要的原料—聚醚对外加剂技术的发展起着重要作用。本文介绍甲氧基聚乙二醇醚、烯丙基聚氧乙烯醚、甲基烯丙基聚氧乙烯醚、异戊烯基聚氧乙烯醚及环氧封端聚乙二醇的制备技术现状及存在的问题,并对传统聚醚合成聚羧酸减水剂的工艺进行简要说明;针对传统聚醚大单体化学改性潜力低的缺点,补充阐述了具有不同拓扑结构聚醚单体的研究现状,并对聚醚大单体的化学改性及其在未来减水剂市场的发展提出展望,对聚醚大单体未来的应用具有一定借鉴作用。

新型两亲性聚氨酯丙烯酸酯大单体的合成及性能研究

以异氟尔酮-二异氰酸酯(IPDI)、聚乙二醇(PEG)、二羟甲基丙酸(DHMPA)、甲基丙烯酸-β-羟乙酯(HEMA)等为原料,合成了一种新型的功能性大单体。该大单体具有两亲性和可聚合性,可用作反应型表面活性剂——可聚合乳化剂,与传统乳化剂 OP-10与十二烷基硫酸钠相比,具有优异的乳化性能和独特功能。

聚羧酸类减水剂中间大分子单体的合成工艺

通过丙烯酸和甲氧基聚乙二醇的酯化,生成了一种具有反应活性的聚羧酸类减水剂中间大分子单体——甲氧基聚乙二醇丙烯酸酯。探讨了各种实验条件对酯化反应的影响,得出了合成甲氧基聚乙二醇丙烯酸酯的最佳工艺条件。

甲基丙烯酸聚乙二醇单甲醚酯大单体的合成与表征

通过甲基丙烯酸甲酯与环氧乙烷的一步乙氧基化开环聚合,制备了末端含有活性双键和亲水性聚氧乙烯结构单元的活性大分子单体。研究了反应参数的影响,确定了最佳合成条件为:采用1%的复合阻聚剂,1.5%~2%的催化剂,反应温度为130℃~140℃,压力为0.4 MPa^0.5 MPa。并采用红外光谱和核磁共振氢谱对所合成的大单体结构进行了分析表征。结果表明,所合成的甲基丙烯酸聚乙二醇单甲醚酯大单体和设定的目标大分子单体结构完全一致。

聚羧酸减水剂聚醚大单体的应用研究进展

对现阶段国内聚醚大单体的行业发展现状进行了简要分析,介绍了现有的主要聚羧酸大单体的品种和市场情况。从不同大单体分子结构的角度,分析了各大单体种类的优缺点和发展方向,并介绍了一种新型聚羧酸减水剂大单体乙二醇单乙烯基聚乙二醇醚(EPEG)。