【作者】 张珍坤； 刘帅宇； 裴晓东； 叶子涵； 昝婷婷； 支雪丽；

【Author】 Zhenkun Zhang;Shuaiyu Liu;Xiaodong Pei;Zihan Ye;Tingtiang Zan;Xueli Zhi;Key Laboratory of Functional Polymer Materials of Ministry of Education,Institute of Polymer Chemistry,College of Chemistry,Nankai University;

【机构】 南开大学化学学院高分子化学研究所功能高分子材料教育部重点实验室；

【摘要】 由于形貌的各向异性,棒状胶体/纳米颗粒或者刚性高分子往往具有丰富的溶致型液晶相行为。深入理解这类颗粒的多级结构和相互作用与其溶致型液晶行为之间的关系是当前的主要科学问题,其研究有助于探索这类有机软物质粒子在制备功能性液晶材料中的应用。我们结合棒状病毒和高分子接枝二者的特性,以长为880纳米,直径仅6.6 nm的纤细且单分散的蛋白质组装体—fd或者M13病毒为骨架,通过多种途径在其表面接枝不同结构的聚合物,构建了几类典型的尺寸单一的聚合物接枝修饰的棒状胶体粒自模型。以fd或者M13病毒本身的溶致型液晶为参考,通过直观测量各向同性-各项异性之间的相转变,手性胆汁型液晶的指纹结构和螺距等宏观参数,考察了所接枝聚合物的不同结构参数对毛发状聚合物纳米粒子液晶行为的影响并与现有的理论做比较。围绕这些研究在以下几个方面取得了的一定的进展。(1)端基功能化的多重响应性聚合物的制备及其对棒状病毒的接枝修饰。发展了一种制备分子量可控其单分散的多重响应性的遥爪型聚合物的方法,将其接枝到棒状病毒表面,构建了多种聚合物-病毒共轭体(Polymer-virus conjugate, PVC)。(2)棒状病毒手性液晶的起源研究。分子结构类似的棒状病毒能形成微观结构截然不同的列型液晶相的物理起源一直是困扰研究人员的一个难题。我们系统研究了温度诱导fd或者M13病毒液晶从手性到非手性的变化,通过多种研究手段揭示了温度诱导的病毒衣壳蛋白的二级结构和堆叠的微秒变化与病毒手性液晶温度响应性之间的关系。(3)聚合物接枝密度对棒状病毒手性液晶的影响。发现了高密度接枝的聚合物之间的立体位阻排斥足以干扰棒状病毒衣壳蛋白的多级结构从而影响其手性液晶行为。(4)具有相互吸引作用的棒状颗粒的液晶行为研究。通过温敏性聚合物接枝修饰棒状病毒,实现了棒状颗粒间的"吸引"但不聚集的可控胶体相互作用,系统研究了粒间吸引相互作用对其液晶行为的影响,从实验的角度论证了理论预测的这类体系的许多特殊液晶相行为。(5)病毒手性液晶的应用。通过在病毒表面引入具有分子识别功能的小分子,如具有糖响应的苯硼酸及其衍生物,赋予棒状病毒的手性液晶的糖响应功能,可用于活性生物小分子的可视化检测。此外,以病毒手性液晶为模板,发展了合适的原位成胶方法,构建了具有内在手性结构的纯聚合物水凝胶。更多还原

【Abstract】 Due to their anisotropic shape,rodlike colloidal/nano particles or rigid polymers exhibit rich lyotropic liquid crystals(LC) behaviors that have attracted broad interest.The main challenge in the study of such behavior is to connect the molecular structure and inter-particle interactions of the mesogens to their mesoscale LC behaviors.Such studies are expected to facilitate the preparation of novel LC materials based on these rodlike particles or polymers.We have combined the unique advantages of filamentous viruses such as fd,M13 and polymer grafting to create several kinds of well-defined polymer-grafted rodlike model particles.Fd or M13 viruses have a highly monodisperse rodlike contour shape with a length of 880 nm and a diameter of 6.6 nm.There are many surface functional groups that offer vast possibilities for chemical modifications.These viruses can form a unique chiral nematic LC(CLC) phase thati s very sensitive to the molecular information of the constitute viruses and inter-virus interactions.The grafted polymers can be exploited to tune such factors by varying the molecular structure and grafting density of the polymers.Using such well-defined polymer-grafted viruses as the model system,we have systematically investigated their isotropic-nematic LC phase transition,changes of the fingerprint and pitch of their CLC phase under various conditions.Results obtained from this project can be summarized as following:(1) Preparation of end-functionalized polymers and their grafting to the virus surface.RAFT polymerization and thiol-ene click chemistry have been exploited to prepare a library of stimuli responsive polymers with a NHS functional group at one of the chain ends.By grafting such polymers onto the surface of the fd or M13 viruses,we have prepared several kinds of well-defined polymer-virus conjugates(PVCs) that can be used as model systems for the afore-mentioned investigations.With one of the PVSs that is grafted with a thermo-and glucose-responsive polymer,nanofibrous hydrogels consisting of the rodlike virus as the main backbone were obtained,which have such properties as reversible sol-to-gel transition,three-dimensional networking and injectability.(2) Influence of the grafting density on the CLC phase of rodlike viruses.We have succeeded in overcoming the low grafting density limitation of the "graft to" method and increased the grafting density of the polymers that are grafted onto the rodlike viruses to such a degree that the grafted polymers are in the brush conformation.We found that fd or M13 viruses with such high grafting density cannot form conventional CLC phase.It is believed that strong inter-chain steric repulsions of the grafted polymers influence the secondary structure of the coating proteins of the virus.The conformation of the viruses might deviate from the super helix state into straight one.(3) Influence of attractions on the LC behaviors of rodlike particles.Theories that deal with the LC behaviors of rodlike particles are based on theassumption that excluded volume repulsion is the only inter-particle interaction although strong attraction often exists between rodlike particles.Experimental study of the LC behavior of rodlike particles that have true interparticle attraction are often hindered due to the attraction induced gelation.We prepared viruses that grated with a block copolymer PEG-b-PNIPAM with the end of the PNIPAM block tethered onto the virus surface.At T > LCST,the PNIPAM block collapses on the virus surface and induces inter-virus attraction while the PEG block offers steric repulsion that prevents inter-virus aggregations.This is the first rodlike model system with tunable attractive interactions.LC behaviors of this system reveal some results that are coexistent with theoretic predictions.(4) Applications of the CLC phase of rodlike viruses.By in-situ gelation of polymer precursors in the presence of the homogenous CLC phase of the virus,hydrogels with embedded chiral structure are prepared.After removing the virus templates under proper conditions,the chiral structure is kept in the pure hydrogels.By monitoring the pitch of the fingerprints of the chiral feature of the hydrogels,we can quantitatively characterize stimulus-responsive behavior of the hydrogels.In addition,we prepared a phenylboronic acid(PBA)decorated M13 virus by convenient surface chemical modifications.The M13–PBA hybrid virus can form either a purenematic or chiral LC(CLC) phase,due to the pH-dependentamphiphilicity of PBA.Under the conditions suitable for the formation of the CLC phase,aromatic diols such as catechol,dopamine etc.can further influence the 3 D ordering of the hybrid virus and induce the formation of the pure nematic LC phase.Such responsive arrangement of the rodlike virus in the presence of varied diols might find applications in the development of sensing materials.更多还原