单一分子量含氟嵌段共聚物的本体及薄膜自组装研究

嵌段共聚物导向自组装作为一种自下而上的图案化工艺,受到工业界和学术界的广泛关注.然而,导向自组装中缺陷率与分子参数之间的关系研究尚不清晰.本文工作基于模块化合成策略,利用迭代指数增长法并结合巯基-双键的点击反应成功制备了高χ低N的单一分子量含氟聚酯嵌段共聚物(oLAn-FPOSS).单一分子量特征可以排除多分散性对自组装行为的影响.本体自组装研究表明聚酯嵌段和含氟嵌段具有强相分离驱动力,可以形成特征尺寸小于10 nm的六方柱状相结构(HEX).在薄膜自组装中,嵌段共聚物经过简单的热退火可以在硅片表面形成平行基底排布的柱状纳米图案.此外,通过对比研究不同链长单一分子量嵌段共聚物的薄膜组装行为,发现随着嵌段共聚物链长的增长薄膜组装图形缺陷率明显下降,初步揭示了薄膜自组装过程中缺陷形成对嵌段共聚物链长的依赖性.

Quantitative understanding of phase segregation behaviors by precisely building discrete oligo-ester-b-oligo-olefin block copolymers

Block copolymers(BCPs) with high Flory-Huggins parameter(χ) and balanced surface energy have aroused tremendous interest for ultra-small nanopatterns processing.However,high χ and balanced surface energy are generally contradicted.The fine tune of chain structure might be a useful way to achieve high χ and balanced surface energy.To realize this,the block copolymer with exactly uniform chain structure,i.e.,defined molecular structure,is highly desirable for accurately evaluating the phase behavior.Herein,two kinds of discrete oligo ester-b-oligo olefin block copolymers with different chemical structures(oligo lactic acid-boligo olefin BCP,oLA_(n)-b-C_(m);oligo phenyl lactic acid-b-oligo olefin BCP,oPL_(n)-b-C_(m)) were modularly synthesized through iterative growth methods.The effect of chain structure on segregation strength and surface properties was quantitatively investigated using the discrete BCPs as precise models.On the one hand,introducing rigid and nonpolar phenyl groups into oligo ester block has a negligible effect on the chemical incompatibility,as confirmed by the identical high χ values of oLA_(n)-b-C_(m) and oPL_(n)-b-C_(m)(χ_(oLA/C)=0.21 and χ_(oPL/C)=0.19).On the other hand,the incorporation of nonpolar phenyl groups creates balanced surface energy,that is,the high χ and balanced surface energy were simultaneously achieved by oPL_(n)-b-C_(m).Therefore,sub-10 nm perpendicular nanopatterns can be easily produced upon brief thermal treatment,demonstrating its potential application in semiconductor manufacturing with ultra-small feature size.The discrete BCP can serve as a quantitative and exquisite model to study the critical contribution of chain structures on phase separation behavior,providing insightful understanding to facilitate the potential application in the chip process.

ANIONIC SYNTHESIS OF A “CLICKABLE” MIDDLE-CHAIN AZIDE-FUNCTIONALIZED POLYSTYRENE AND ITS APPLICATION IN SHAPE AMPHIPHILES

＂Click chemistry＂ is, by definition, a general functionalization methodology （GFM） and its marriage with living anionic polymerization is particularly powerful in precise macromolecular synthesis. This paper reports the synthesis of a ＂clickable＂ middle-chain azide-functionalized polystyrene （mPS-N3） by anionic polymerization and its application in the preparation of novel shape amphiphiles based on polyhedral oligomeric silsesquioxane （POSS）. The mPS-N3 was synthesized by coupling living poly（styryl）lithium chains （PSLi） with 3-chloropropylmethyldichlorosilane and subsequent nucleophilic substitution of the chloro group in the presence of sodium azide. Excess PSLi was end-capped with ethylene oxide to facilitate its removal by flash chromatography. The raPS-N3 was then derived into a giant lipid-like shape amphiphile in two steps following a sequential ＂click＂ strategy. The copper（I）-catalyzed azide-alkyne cycloaddition between mPS-N3 and alkyne-functionalized vinyl-substituted POSS derivative （VPOSS-alkyne） ensured quantitative ligation to give polystyrene with VPOSS tethered at the middle of the chain （mPS-VPOSS）. The thiol-ene reaction with 1-thioglycerol transforms the vinyl groups on the POSS periphery to hydroxyls, resulting in an amphiphilic shape amphiphile, mPS-DPOSS. This synthetic approach is highly efficient and modular. It demonstrates the ＂click＂ philosophy of facile complex molecule construction from a library of simple building blocks and also suggests that mPS-N3 can be used as a versatile ＂clickable＂ motif in polymer science for the precise synthesis of complex macromolecules.

Changes of Secondary Metabolites and Trace Elements in Gentiana macrophylla Flowers: A Potential Medicinal Plant Part

Objective To search for the potential medicinal plant part of Gentiana macrophyllabased on changes of secondary metabolites and trace elements in the flowers of G.macrophylla.Methods HPLC was used to detect the changes of the active constituents（longanic acid,sweroside,gentiopicroside,and swertiamarin）and ICP-AES was used for mineral nutrients in G.macrophylla during flower development.And soluble sugar,starch,crude protein,hemicelluloses,cellulose,and lignin were determined.Results Biomass of flower in full bloom（D2）phase was considerable during flower development,in which the contents of longanic acid and gentiopicroside were at the highest levels with 2.65 and 2.88 times higher than those recorded in Chinese Pharmacopoeia 2010,sweroside and swertiamarin in the flowers were reaching 6.06 and 1.25 times higher than those in roots.Florescence is the most valuable stage during flower development.The concentration of Fe,Mg,K,P,and B was higher in the flowers than that in roots.The accumulation of active constituents in the plant was influenced by the contents of metabolically linked carbon and nitrogen compounds.Conclusion The secondary metabolites,mineral nutrients,and physicochemical indicators are tightly regulated by flower organ development,D2 is an important stage for both biomass and extraction of active constituents such as longanic acid.The flowers of G.macrophylla could be used as a potential medicinal plant part for longanic acid at a high level.

Two-dimensional assembly of giant molecules

This mini review summarizes recent progress on two-dimensional(2 D) self-assembly of giant molecules. Two critical factors with significant impact on the formation of nanostructure are highlighted, i.e., the dimensional constraint of 2 D geometry, and the conformational constraint imposed the rigid molecular nanoparticles(MNPs). Diverse 2 D nanostructures have been fabricated in condensed state and solution by rational molecular design. The collective secondary interactions between functional groups on the periphery of the MNPs and their persistent shape, together with the dimensional limit, change the free energy landscape and lead to unconventional nanostructures. The unique molecular properties of giant molecules endow these 2 D structures with promising technological applications.