Synthesis and characterization of miktoarm star copolymer of styrene and butadiene using multifunctional macromolecular initiator

A new kind of multifunctional macromolecular initiator with Sn-C bonds and polydiene arms was synthesized by living anionic polymerization. At first, polydiene-stannum chloride （PD-SnCl3） was prepared by the reaction of n-butyl-Li （n-BuLi）, stannic chloride （SnCl4） and diene. Then PD-SnCl3 was used to react with the dilithium initiator to prepare the multifunctional organic macromolecular initiators. The result suggested that the initiators had a remarkable yield by GPC, nearly 90%. By using these multifunctional macromolecular initiators, styrene and butadiene were effectively polymefized via anionic polymerization, which gave birth to novel miktoarm star copolymers. The relative molecular weight and polydispersity index, microstructure contents, copolymerization components, glass transition temperature （Tg） and morphology of the miktoarm star copolymers were investigated by GPC-UV, ~H NMR, DSC and TEM, respectively. 2009 Xing Ying Zhang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Synthesis and performance of miktoarm star copolymers of styrene and butadiene

A novel multifunctional macromolecular organolithium initiator （PD-Sn-（RLi）3） was prepared via living anionic polymerization and used for the synthesis of miktoarm star copolymers in cyclohexane. The average molecular weight, polydispersity index, microstructure and unit composition of the miktoarm star copolymers were characterized with GPC and 1H-NMR. Performances of the miktoarm star styrene-butadiene rubbers were investigated in comparison with those of the blend rubbers such as the tin-coupled star-shaped random copolymers of styrene-butadiene rubber（S-SBR）/natural rubber （NR） blend rubber and S-SBR/Cis-1, 4-polybutadiene rubber （Cis-BR） blend rubber.

DRUG AND PLASMID DNA CO-DELIVERY NANOCARRIERS BASED ON ABC-TYPE POLYPEPTIDE HYBRID MIKTOARM STAR COPOLYMERS

We report on the fabrication of self-assembled micelles from ABC-type miktoarm star polypeptide hybrid copolymers consisting of poly（ethylene oxide）, poly（L-lysine）, and poly（e-caprolactone） arms, PEO（-b-PLL）-b-PCL, and their functional applications as co-delivery nanocarriers of chemotherapeutic drugs and plasmid DNA. Miktoarm star copolymer precursors, PEO（-b-PZLL）-b-PCL, were synthesized at first via the combination of consecutive ＂click＂ reactions and ring-opening polymerizations （ROP）, where PZLL is poly（e-benzyloxycarbonyl-L-lysine）. Subsequently, the deprotection of PZLL arm afforded amphiphilic miktoarm star copolymers, PEO（-b-PLL）-b-PCL. In aqueous media at pH 7.4, PEO（-b-PLL）-b-PCL self-assembles into micelles consisting of PCL cores and hydrophilic PEO/PLL hybrid coronas. The hydrophobic micellar cores can effectively encapsulate model hydrophobic anticancer drug, paclitaxel; whereas positively charged PLL arms within mixed micellar corona are capable of forming electrostatic polyplexes with negatively charged plasmid DNA （pDNA） at N/P ratios higher than ca. 2. Thus, PEO（-b-PLL）-b-PCL micelles can act as co-delivery nanovehicles for both chemotherapeutic drugs and genes. Furthermore, polyplexes of pDNA with paclitaxel-loaded PEO（-b- PLL）-b-PCL micelles exhibited improved transfection efficiency compared to that of pDNA/blank micelles. We expect that the reported strategy of varying chain topologies for the fabrication of co-delivery polymeric nanocarriers can be further applied to integrate with other advantageous functions such as targeting, imaging, and diagnostics.

Preferentially released miR-122 from cyclodextrin-based star copolymer nanoparticle enhances hepatoma chemotherapy by apoptosis induction and cytotoxics efflux inhibition

Chemotherapy,as one of the most commonly used treatment modalities for cancer therapy,provides limited benefits to hepatoma patients,owing to its inefficient delivery as well as the intrinsic chemo-resistance of hepatoma.Bioinformatic analysis identified the therapeutic role of a liver-specific microRNA-miR-122 for enhancing chemo-therapeutic efficacy in hepatoma.Herein,a cyclodextrin-cored star copolymer nanoparticle system(sCDP/DOX/miR-122)is constructed to co-deliver miR-122 with doxorubicin(DOX)for hepatoma therapy.In this nanosystem,miR-122 is condensed by the outer cationic poly(2-(dimethylamino)ethyl methacrylate)chains of sCDP while DOX is accommodated in the inner hydrophobic cyclodextrin cavities,endowing a sequential release manner of miR-122 and DOX.The preferentially released miR-122 not only directly induces cell apoptosis by down regulation of Bcl-w and enhanced p53 activity,but also increases DOX accumulation through inhibiting cytotoxic efflux transporter expression,which realizes synergistic performance on cell inhibition.Moreover,sCDP/DOX/miR-122 displays remarkably increased anti-tumor efficacy in vivo compared to free DOX and sCDP/DOX alone,indicating its great promising in hepatoma therapy.

Amphiphilic miktoarm star copolymers can self-assemble into micelle-like aggregates in nonselective solvents: a case study of polyoxometalate based miktoarm stars

It is well-known that amphiphilic star-shaped copolymers can self-assemble in selective solvents to form complicated micellar constructs as a synergistic result of both the topological constraints and relative volume fractions of the arms.Although the association phenomena of amphiphilic stars have been observed in nonselective solvents,both the structural detail and formation mechanism of these associates are not clear yet.Moreover,these experimental observations are controversial with respect to molecularly dispersed starlike copolymers in nonselective solvents as is popularly believed.To clarify these issues,we have synthesized a series of polyoxometalate-based polystyrene-poly(ethylene glycol)(PS-PEG)miktoarm star supramolecular copolymers(SEW-1–5)by coupling a Keggin-type polyoxometalate of K4[α-SiW12O40]with 1,2,3-triazolium bridged block copolymers of-PSn-b+-PEGmI-(n=17,26,39,57,81;m=45)through ionic exchange reactions,respectively.TEM imaging,contact angle and 1H NMR studies reveal that SEW-2–5 self-assemble in chloroform,THF,and toluene to create micellelike aggregates ranging from cylinder to sphere with a PS corona and a PEG core,while for SEW-1,reverse bilayers are captured with a PEG corona and a PS core.Among these aggregates,the Keggin clusters of[α-SiW12O40]4-localize at the core-corona interfaces between PS and PEG.In terms of solvent quality,chloroform,THF,and toluene are only slightly poorer for PEG than that for PS with a relative order of chloroform<THF<toluene.These unexpected aggregates originate from the topological constraints of the chemically different arms of PS and PEG in the miktoarm stars,where the weak incompatibility between the PS and PEG arms is intensified appropriately.The presence of the reverse bilayered structures of SEW-1 is due to the magnified steric hindrance of the PEG45 arm with decreasing the molecular weight of the PS17 arm.However,to the best of our knowledge,these are the first examples clearly indicating that miktoarm star copolymers can self-assemble in common good solvents or slightly selective solvents to generate micellelike aggregates.This scenario is not only in sharp contrast to the intuitively considered behavior of unimolecular miktoarm stars in nonselective solvents,but also rather different from the conventional selfassembly behavior of amphiphilic star copolymers in selective solvents.

Morphologies of Core-Shell-Cylinder-Forming ABC Star Triblock Copolymers in Nanopores

The self-assembly behavior of ABC star triblock copolymers can lead to a large number of nanostructures. Indeed, many new and interesting structures have already been discovered and proven to be hotspot in soft matter physics research. In this work, we introduce different phase diagrams of core-shell-cylinder-forming ABC star triblock copolymers under different conditions, including in-bulk and pore geometries with different sizes. The relation between the pore size geometries and their corresponding structures are also revealed. The different properties of the surface potential field that significantly affect the self-assembly process of ABC star triblock copolymers are investigated as well.

Synthesis of Self-assembled Star/Linear Block Copolymer Blends via Aqueous RAFT Dispersion Polymerization

Reversible addition-fragmentation chain transfer(RAFT)-mediated polymerization-induced self-assembly(PISA)of star block copolymer and linear block copolymer using a binary mixture of a star-like macro-RAFT agent and a linear macro-RAFT agent is reported.With this formulation,star block copolymer and diblock copolymer were formed simultaneously to generate colloidally stable star/linear block copolymer assemblies.Size exclusion chromatography(SEC)analysis confirmed the presence of two types of polymers in the final samples.The molar ratio of the star-like macro-RAFT agent and the linear macro-RAFT agent has a significant impact on the morphology of polymer assemblies.It was found that increasing the amount of star-like macro-RAFT agent facilitated the formation of higher-order morphologies.Additionally,effects of other reaction parameters including the length/number of the arm of the star-like macro-RAFT agent,degree of polymer(DP),monomer concentration on the morphology of star/linear block copolymer assemblies were also investigated.We expect that this work will offer new possibilities for the scalable preparation of polymer assemblies with unique structures and functions.

Morphology and Properties of Miktoarm Star Styrene-Butadiene Rubber

In order to obtain the optimized structure rubber, a novel miktoarm star styrene-butadiene rubber （MS- SBR） was initiated by a multifunctional macromolecular initiator with polydiene arm and Sn-C bond. The properties of MS-SBR were investigated with respect to the morphology, mechanical properties, and dynamic viscoelasticity in comparison with those of the blends, natural rubber （NR）/star styrene-butadiene random rubber （S-SBR） blend rubber and cis-l,4-polybutadiene rubber （cis-BR）/S-SBR blend rubber. The samples were analyzed using transmission elec- tron microscopy （TEM）, dynamic mechanical thermal analyzer （DMTA）, and mechanical properties test. The analy- sis results show that MS-SBR possesses the desired combination of low rolling resistance and high antiskid resistance, and is promising for application in high performance tire tread.

Nanoparticle-filled ABC Star Triblock Copolymers:A Dissipative Particle Dynamics Study

The phase behavior of nanoparticle-filled ABC star triblock copolymers was investigated by dissipative particle dynamics simulation.Two typical structures,the three-color lamella and polygonal tiling structures,were selected to demonstrate the effect of filling the nanoparticle.Results showed that the filling effects were obvious on the lamellar structure but not on the tiling structure,where the high concentration of fillers can destroy the lamellar structures.The dynamic processes of nanoparticle filling were investigated for the lamellar and tiling structures,where three stages can be sorted by analyzing the system energies and chain conformations.Moreover,the mechanical properties were evaluated for the lamellar structures by exploring the interface tensions.The findings can help us understand the potential applications of microstructures based on complex block copolymers and nanoparticle mixtures.

半连续RAFT反相乳液共聚合制备星型阳离子聚丙烯酰胺

首次提出采用"臂先"方法的丙烯酰胺(AM)、甲基丙烯酰氧乙基三甲基氯化铵(DMC)及N,N’-亚甲基双丙烯酰胺(BisAM)的半连续RAFT反相乳液共聚合方法制备星型阳离子聚丙烯酰胺(sCPAM),该聚合物具有阳离子链段集中在含超支化聚丙烯酰胺(PAM)核的臂末端的结构。通过控制AM和BisAM的加料以及AM与RAFT链转移剂的比例,合成了不同臂长、超支化PAM核及臂末端阳离子组成的sCPAM。研究表明在使用BisAM与AM和DMC摩尔比为2～5:1600的低二烯类单体用量条件下,高效制备了臂数为2.5～6.9、星型聚合物含量高达92.9%的sCPAM。TiO2浊液絮凝研究表明提高星型结构含量以及臂末端阳离子密度的sCPAM具有更好的絮凝效果,絮凝性能优于具有更高阳离子度与分子量的线性无规阳离子聚丙烯酰胺工业絮凝剂C535M。

Resorcinarene-centered Amphiphilic Star-block Copolymers: Synthesis, Micellization and Controlled Drug Release

Eight-arm star-shaped poly（■-caprolactone）-block-poly（ethylene glycol）s（SPCL-b-PEG） have been prepared by a combination of controlled ring-opening polymerization（CROP） and coupling reaction. First, eight-arm star-shaped poly（■-caprolactone）s（SPCL） with a resorcinarene core were synthesized using octamethyl tetraundecylresorcinarene octaacetate as octa-initiator and yttrium tris（2,6-di-tert-butyl-4-methylphenolate） [Y（DBMP）3] as catalyst. Then the coupling reaction was carried out between SPCLs and carboxyl-terminated methoxy poly（ethylene glycol）s（mP EG-COOH） in the presence of N,N′-dicyclohexylcarbodiimide（DCC） and 4-dimethylaminopyridine（DMAP）, resulting in eight-arm star-shaped SPCL-b-PEGs with controlled molecular weight and well-defined architecture. Furthermore, these amphiphilic eight-arm SPCL-b-PEGs could self-assemble into micelles with low critical micellar concentrations（CMC）, which was characterized by fluorescent spectroscopy. Moreover, indomethacin loaded micelles with high drug loading content and high encapsulation efficiency can be prepared, which is probably due to the highly branched architecture. The morphologies of micelles were characterized by transmission electron microscopy（TEM）, which exhibited diverse nanostructures as the drug loading contents varied. In vitro drug release of indomethacin from SPCL-b-PEG micelles was carried out in PBS, from which a sustained release behavior was observed. SPCL-b-PEG micelles did not show significant cytotoxicity at copolymer concentrations up to 1000 mg/L, making them very promising for drug delivery.

Surface-induced Morphologies of ABC Star Triblock Copolymer in Spherical Cavities

The morphologies and phase diagrams exhibited by symmetric ABC star triblock copolymer nanoparticles are investigated on the basis of real-space self-consistent field theory. The ABC star triblock copolymers were chosen to be tiling-forming with fixed polymer parameter and the spherical boundaries were modeled using the masking technique. We first study a number of examples where the ABC triblock copolymers confined in spherical cavities with neutral surface. Then, two types of spherical cavity distinct preferential surfaces are considered, including both A-block attractive and repulsive preferential surfaces. We aim at the effects due to various spherical cavity diameters and the degree of interactions between the polymer and the spherical surface. A variety of morphologies, such as ring-like structures, concentric sphere, and irregular cylinder, were identified in phase diagrams. The results show that both the degree of interactions and spherical diameters can influence the formation of morphologies so that ring-like structures and other novel structures could be obtained.

Synthesis and Self-assembly of a Triarm Star-shaped Rod-Rod Block Copolymer

We designed and synthesized a triarm star-shaped rod-rod block copolymer（BCP）,（poly{2,5-bis[（4-methoxyphenyl）-oxycarbonyl]styrene}-block-poly（γ-benzyl-L-glutamate））3,（PMPCS-b-PBLG）3. The triarm core with three PMPCS-N3 segments was prepared by copper-mediated atom transfer radical polymerization of 2,5-bis[（4-methoxyphenyl）-oxycarbonyl]styrene initiated by a trifunctional initiator and a subsequent azide reaction. And the PBLG block with alkyne functionality was synthesized through ring-opening polymerization of γ-benzyl-L-glutamate N-carboxyanhydride initiated by propargylamine. Finally, Huisgen＇s 1,3-dipolar cycloaddition was employed to combine the triarm（PMPCS-N3）3 and PBLG segments. The chemical structure of the BCP was confirmed by 1H-NMR spectroscopy, Fourier-transform infrared spectroscopy, and gel permeation chromatographic analysis. Results from differential scanning calorimetry, polarized light microscopy, one-dimensional and two-dimensional wide-angle X-ray diffraction, and transmission electron microscopy techniques demonstrate that the triarm star-shaped rod-rod BCP self-assembles into a hexagon-in-lamella morphology, with the PMPCS block in the columnar nematic phase and the PBLG block in the hexagonal columnar arrangement packed in bilayers due to the rigid nature of the two blocks and the covalent connections in the star-shaped BCP.

Amphiphilic Seven-arm Star Triblock Copolymers with Diverse Morphologies in Aqueous Solution Induced by Crystallization and pH

Well-defined amphiphilic seven-arm star triblock copolymers containing hydrophobic crystalline poly（e-caprolactoneXPCL） blocks, hydrophobic non-crystalline poly（tert-butyl acrylate）（PtBA） blocks and hydrophilic poly（ethylene glycol）（PEG） blocks were precisely synthesized by a combination of ring-opening polymerization（ROP）, atom transfer radical polymerization（ATRP） and ＂click＂ reaction. Such star copolymers could self-assemble into ＂core-shell-corona＂ micelles and ＂multi-layer＂ vesicles depending on the fraction of each block. Meanwhile, the selective hydrolysis of middle PtBA blocks into the poly（acrylic acidXPAA） blocks allowed the star block copolymers to further change their morphologies of aqueous aggregates m response to pH values.

Self-assembling Characteristics of Amphiphilic Star Block Copolymers with a Polyelectrolyte Shell

1 Results Amphiphilic block copolymers are capable of forming supramolecular assemblies resembling those observed in nature,such as spherical micelles,worm micelles,and vesicles.Changing the solvent composition,ionic strength or pH of the polymer solution may induce the self-assembly of block copolymers or trigger the transition between the geometries of noncovalent assemblies.In the current work,we have synthesised starlike amphiphilic block copolymers having hydrophobic poly(methyl methacrylate),PMMA,...

生物医用材料脂肪族聚酯的改性和应用研究

生物医用材料脂肪族聚酯具有优良的生物相容性、可再生性、可吸收性以及生物可降解性等特点,在医疗、医药、组织工程以及医学检测等领域受到了广泛的关注。通过接枝改性等方法引入具有一定特殊性能的功能基团或改变聚合物的形状,可以改善脂肪族聚酯的性能,获得更加广泛的用途。简述了脂肪族聚酯及其特性,对其改性方法进行了论述,对其实际应用进行了简要介绍,最后对脂肪族聚酯的应用前景及发展趋势进行了展望。