Heavy Metal Ions Removal by Nano-sized Spherical Polymer Brushes

Nano-sized spherical polymer brushes （SPBs） consisting of both a polystyrene （PS） core and a brush shell of poly（acrylic acid） （PAA）, poly（N-acrylcysteamine） （PSH）, or poly（N-acrylcysteamine-co-acrylic acid） （P（SH-co-AA））, were prepared by photo-emulsion polymerization. The core-shell structure was observed by dynamic light scattering and transmission electron microscopy. Due to the strengthened Donnan effect, the PAA brush can adsorb heavy metal ions. Effects of the contact time, thickness of PAA brush and pH value on the adsorption results were investigated. Due to the coordination between the mercapto groups and heavy metal ions as well as the electrostatic interactions, SPBs with mercapto groups are capable to remove heavy metal ions selectively from aqueous solutions. The order of adsorption capacity of the heavy metal ions by SPBs with mercapto groups is： Hg2＋ ≈ Au3＋ 〉 Pb2＋ 〉 CH2＋ 〉 Ni2＋. The adsorbed heavy metal ions can be eluted from SPB by aqueous HCI solution, and the SPBs can be recovered. After three regenerations the recovered SPBs still maintain their adsorption capacity.

On the friction and adhesion hysteresis between polymer brushes attached to curved surfaces: Rate and solvation effects

Computer simulations of friction between polymer brushes are usually simplified compared to real systems in terms of solvents and geometry.In most simulations,the solvent is only implicit with infinite compressibility and zero inertia.In addition,the model geometries are parallel walls rather than curved or rough as in reality.In this work,we study the effects of these approximations and more generally the relevance of solvation on dissipation in polymer-brush systems by comparing simulations based on different solvation schemes.We find that the rate dependence of the energy loss during the collision of brush-bearing asperities can be different for explicit and implicit solvent.Moreover,the non-Newtonian rate dependences differ noticeably between normal and transverse motion,i.e.,between head-on and off-center asperity collisions.Lastly,when the two opposing brushes are made immiscible,the friction is dramatically reduced compared to an undersaturated miscible polymer-brush system,irrespective of the sliding direction.

Cylindrical polymer brushes-anisotropic unimolecular micelle drug delivery system for enhancing the effectiveness of chemotherapy

Polymer systems can be designed into different structures and morphologies according to their physical and chemical performance requirements,and are considered as one of the most promising controlled delivery systems that can effectively improve the cancer therapeutic index.However,the majority of the polymer delivery systems are designed to be simple spherical nanostructures.To explore morphology/size-oriented delivery performance optimization,here,we synthesized three novel cylindrical polymer brushes(CPBs)by atom transfer radical polymerization(ATRP),which were cellulose-g-(CPT-b-OEGMA)(CCO)with different lengths(~86,~40,and~21 nm).The CPBs are composed of bio-degradable cellulose as the carrier,poly(ethylene glycol)methyl ether methacrylate(OEGMA)as hydrophily block,and glutathione(GSH)-responsive hydrophobic camptothecin(CPT)monomer as loaded anticancer drug.By controlling the chain length of the initiator,three kinds of polymeric prodrugs with different lengths(CCO-1,CCO-2,and CCO-3)could be self-organized into unimolecular micelles in water.We carried out comparative studies of three polymers,whose results verified that the shorter CPBs exhibited higher drug release efficiency,more cellular uptake,and enhanced tumor permeability,accompanied by shortened blood circulation time and lower tumor accumulation.As evidenced by in vivo experiments,the shorter CPBs exhibited higher anti-tumor efficiency,revealing that the size advantage has a higher priority than the anisotropic structure advantage.This provided vital information as to design an anisotropic polymer-based drug delivery system for cancer therapy.

A Facile and Environment-friendly Method for Fabrication of Polymer Brush

A novel environment-friendly system is proposed to fabricate polymer brush, which has the advantages including non-toxic and inexpensive initiator （eosin Y）, visible-light exposure （λ = 515 nm）, water medium and ambient environment. The experimental results from UV-Vis spectroscopy, AFM-based single molecule force spectroscopy （SMFS） and other measurements indicate that a polymer brush with a living nature is fabricated via free radical polymerization. This polymer brush may find applications in coatings, bio-interfaces and so forth.

Biocompatible hierarchical zwitterionic polymer brushes with bacterial phosphatase activated antibacterial activity

Hierarchical polymer brushes have been considered as an effective and promising method for preventing implant-associated infections via multiple antibacterial mechanisms.Herein,a bacterial phosphatase re-sponsive surface with hierarchical zwitterionic structures was developed for timely dealing with the poly-meric implant-associated bacterial infection.The hierarchical polymeric architecture was subtly realized on model polypropylene(PP)substrate by sequential photo living grafting of poly(2-(dimethylamino)ethyl methacrylate(PDMAEMA)bottom layer and zwitterionic poly(sulfobetaine methacrylate)(PSBMA)upper layer,followed by the conversion of the PDMAEMA into the zwitterionic structure via succes-sive quaternization and phosphorylation reactions.Owing to shielding the bottom polycations,the hi-erarchical zwitterionic polymer brushes guaranteed the surface with the optimal biocompatibility under the normal physiological environment.Once bacteria are invaded,the surface bactericidal activity of the bottom layer can be rapidly and automatically activated owing to the transition triggered by bacterial phosphatase from zwitterion to polycation.Additionally,ameliorated by the upper layer,the hierarchical surface showed obvious adhesion resistance to dead bacterial cells and notably migrated the cytotoxic-ity of exposed polycation after completion of the bactericidal task.As a proof-of-principle demonstration,this self-adaptive hierarchical surface with sensitive bacterial responsiveness and biocompatibility showed great potential in combating hernia mesh-related infection.This work provides a promising and universal strategy for the on-demand prevention of medical device-associated infections.

How Does a Polymer Brush Repel Proteins?

The captioned question has been addressed by the steric effect; namely, the adsorption of proteins on a surface grafted with linear polymer chains decreases monotonically as the grafting density increases. However, there is no quantitative and satisfactory explanation why the adsorption starts to increase when the grafting density is sufficiently high and why polyethylene glycol（PEG） still remains as one of the best polymers to repel proteins. After considering each grafted chain as a molecular spring confined inside a ＂tube＂ made of its surrounding grafted chains, we estimated how its free energy depends on the grafting density and chain length, and calculated its thermal energy-agitated chain conformation fluctuation, enabling us to predict an adsorption minimum at a proper grafting density, which agrees well with previous experimental results. We propose that it is such a chain fluctuation that slows down the adsorption kinetically.

Structures and Surface States of Polymer Brushes in Good Solvents:Effects of Surface Interactions

The influence of the surface interaction on the mesoscopic structure of grafted polymers in good solvents has been examined. At high surface coverage, tethered polymers are in the brush state and the parabolic segment density profile is confirmed by self-consistent field theory （SCFT） calculations. It is found that this is a universal behavior for a whole range of surface interactions from complete repulsion to strong attraction. More interestingly, finite surface repulsion may lead to the maximum in the proximal layer of its segment density profile, which is significantly different from both the depletion layer of pure repulsion and the adsorbing layer of attraction. In addition to the brush state on both repulsive and attractive surfaces, three additional surface states were identified by analyzing the scaling behavior of the layer thickness of polymer brushes： the mushroom state on repulsive substrates, the dilute and the semidilute surface states on attractive substrates.

PIEZOELECTRIC PROPERTIES OF SINGLE-STRAND DNA MOLECULAR BRUSH BIOLAYERS

The paper is devoted to investigations on nanomechanical behaviors of biochips in label-free biodetections. The chip consists of Si-layer, Ti-layer, Au-layer and single-strand DNA （ssDNA） molecular brush biolayer immobilized by self-assembly technology of thiol group. Unlike previous viewpoints, such as force-bending, entropy-bending and curvature electricity effect, etc., the piezoelectric effect of the biopolymer brush layer is viewed as the main factor that induces nanomechanical bending of biochips, and a classical macroscopic piezoelectric constitutive relation is used to describe the piezoelectric effect. A new laminated cantilever beam model with a piezoelectric biolayer in continuum mechanics, the linearized Poisson-Boltzmann equation in statistical mechanics and the scaling method in polyelectrolyte brush theory are combined to es- tablish a relationship between the nanomechanical deflection of DNA chips and the factors such as nanoscopic structural features of ssDNA molecules, buffer salt concentration, macroscopic mechanical/piezoelectric parameters of DNA chips etc. Curve fitting of experimental data shows that the sign of the piezoelectric constant of the biolayer may control the deflection direction of DNA chips during the packaging process.

Tuning Polymer-Grafted Particle Monolayer Structure at the Air-Water Interface by Introducing Anisotropic Features

Fabrication of anisotropic material is one of the important topics and we examined to introduce “anisotropic” nature by spreading polymer-grafted particle on the medium with polymer-reactive potential. Poly (tert-butyl methacrylate) (PtBMA) was polymerized from polystyrene latex (PSL) surface by ATRP to give PtBMA-grafted PSL (PSL-PtBMA). Particle monolayer was formed at air-water and air-acidic water interfaces and the monolayer characteristics were compared by π-A isotherm measurements, SEM observations, and contact angle measurements. π-A isotherms, in particular, indicates that the interaction between polymer chains become stronger by changing the subphase condition, which suggests that anisotropicparticle monolayer formation.

Formation of surface-attached microstructured polyelectrolyte brushes

平面稳固的表面上的依附表面的 micropatterned 聚合电解质刷子用由自我装配的开始者单层开始相片的免费激进的聚合被产生。形成的模式能与不同 patterning 过程否定或积极，这被显示出。

Simultaneous Bulk-and Surface-initiated Living Polymerization Studied with a Heterogeneous Stochastic Reaction Model

To better characterize the properties of surface-initiated polymers, simultaneous bulk-and surface-initiated polymerizations are usually carried out by assuming that the properties of the surface-initiated polymers resemble those of the bulk-initiated polymers. Through a Monte Carlo simulation using a heterogeneous stochastic reaction model, it was discovered that the bulk-initiated polymers exhibit a higher molecular weight and a lower dispersity than the corresponding surface-initiated polymers, which indicates that the equivalent assumption is invalid. Furthermore, the molecular weight distributions of the two types of polymers are also different, suggesting different polymerization mechanisms. The results can be simply explained by the heterogeneous distributions of reactants in the system. This study is helpful to better understand surface-initiated polymerization.

氮氧自由基功能性聚合物涂层用于抗贻贝粘附

为了研究氮氧自由基聚合物刷层的抗贻贝粘附性能,利用SI-Cu 0CRP策略,在引发剂修饰表面接枝PTEMPMA刷子,进一步通过氧化得到了含氮氧自由基的PTEMPOMA聚合物刷涂层,并将涂层用于抗贻贝粘附。利用接触角仪、扫描探针显微镜、电子顺磁共振光谱仪、傅里叶红外光谱仪、3D光学轮廓仪等对聚合物刷进行物理和化学性质的表征,通过多巴胺溶液浸泡实验以及真实的贻贝浸泡实验来研究贻贝粘附过程。结果表明:PTEMPMA聚合物刷可以成功接枝在不同基底(如硅片、石英玻璃、不锈钢片、铝片)上,并且可以通过控制反应时间控制聚合物刷涂层的厚度;有效的氧化过程可以得到含有氮氧自由基的PTEMPOMA聚合物刷层,经过贻贝浸泡测试,聚合物刷涂层展现了极好的抗贻贝粘附效果。

原子转移自由基聚合法制备聚合物刷

介绍了原子转移自由基聚合法(ATRP)制备聚合物刷(平面刷、球形刷和分子刷)的研究进展及应用前景。聚合物刷子的奇异构象使其具有许多新奇的性质和潜在的应用前景。ATRP 是制备具有可控结构的聚合物以及有机/无机杂化材料的一种较好的方法。通过 ATRP 制备聚合物刷,可以有效地改变聚合物刷的组成和聚合度,从而改变聚合物刷的表面性质,设计出具有新型结构及性能的材料。

聚合物分子刷的合成与应用

本文综述了近年来在线形聚合物、树枝状大分子及树枝化聚合物等不同聚合物的每个重复单元上,高密度地、通过不同联接方式接枝上新的聚合物侧链而形成的刷形接枝共聚物,即聚合物分子刷的研究进展。主要介绍聚合物分子刷的三种合成途径,即“大单体聚合法”,“从主链接枝法”及“接枝到主链法”,并对不同路线的特点进行分析,同时对分子刷在制备纳米杂化材料、纳米导线及智能材料等方面的应用进行了综述。

聚合物“刷子”的研究进展

采用活性聚合方法在材料表面制备聚合物“刷子”可有效控制材料表面性质,在分子结构设计中具有突出的优越性,所制备“刷子”的分子量可控、分布窄,近年来引起了研究者的广泛关注。主要综述了聚合物“刷子”的各种制备方法。

金表面聚合物刷及图案化微结构的制备

采用表面引发室温原子转移自由基聚合 (ATRP)方法在金基底上原位制备了接枝聚合物刷 ,其制备过程用厚度测量 ,ATR FTIR ,XPS等进行了表征 ,初始时聚合物刷的厚度随着聚合时间的增加线性增加 ,表现为活性聚合的特征 .XPS表征证明表面引发聚合后聚合物刷末端仍然存在ATRP反应的引发剂 .紫外光刻图案化的聚合物刷作为电沉积的模板 ,经电沉积、后紫外处理、湿化学刻蚀步骤后得到了分离的导电聚合物微阵列结构 ,通过浇注 /粘附处理将导电聚合物微阵列转移至硅油弹性体片 ,由于导电聚合物在湿化学刻蚀中对基底金具有良好的保护作用 ,因此在导电聚合物阵列被转移后 ,基底表面得到金微阵列 .

由平面合成聚合物刷——表面引发原子转移自由基聚合研究进展

原子转移自由基聚合反应(ATRP)是实现活性聚合,获得可控聚合物的一种有效途径。通过表面引发原子转移自由基聚合,在材料表面合成聚合物刷,是改变材料表面特征的有效方法。本文综述了表面引发原子转移自由基聚合合成聚合物刷及其最新进展。

玻璃表面聚苯乙烯“刷子”的制备与表征

采用原位活性接枝聚合反应在玻璃表面制备了聚苯乙烯"刷子"层,制备过程包括:将偶联剂3-甲基丙烯酰氧基丙基三甲氧基硅烷接枝到玻璃表面,然后以4-羟基-2,2,6,6-四甲基哌啶氧自由基(HTEMPO.)为自由基捕捉剂,过氧化苯甲酰(BPO)为引发剂,在玻璃表面引发苯乙烯接枝聚合反应,制备了4nm～28nm厚的聚苯乙烯"刷子"。X射线光电子能谱(XPS)表明Si(1s/2p)在99eV、151eV处吸收峰强度随接枝反应时间的延长而逐渐减弱,C(1s)在285eV处的吸收峰强度随接枝时间的延长而增强;椭圆偏振仪结果表明聚苯乙烯层的厚度随聚合时间的延长从4nm增加到28nm。红外光谱(FT-IR)表明在玻璃表面的聚合物为聚苯乙烯。

2，3，4，5，6-五氟苯乙烯聚合物刷的制备和表征

用原子转移自由基聚合方法在硅片表面制备了2,3,4,5,6-五氟苯乙烯聚合物刷.利用椭圆偏正光测厚仪、接触角测定仪和X射线光电子能谱仪对薄膜结构进行了表征.

铜表面聚合物刷的制备及其电化学性能

采用N-[亚苄基-1,2-乙二氨基乙基]-2-溴异丁酰胺为引发剂,联吡啶为配体,溴化亚铜为催化剂,实现了铜表面引发甲基丙烯酸甲酯原子转移自由基聚合,在铜表面形成一层聚甲基丙烯酸甲酯(PMMA)聚合物刷,在0.5mol/L NaCl介质中,采用极化曲线和电化学阻抗法,考察了聚合物刷的电化学性能。结果表明,铜表面接枝的PMMA分子量达到1.27×10~5时,腐蚀电位提高到22mV,腐蚀电流密度降低到0.88μA/cm^2,缓蚀效率达到96.61%,膜的电容值为0.398×10^(-7)F/cm^2,在0.5mol/L NaCl溶液中浸泡24h后,NaCl水溶液渗透进入PMMA薄膜的百分比为77.06%。