CONTROLLED SYNTHESIS OF AMPHIPHILIC BLOCK POLYMERS HAVING GLUCOSE RESIDUES AND THEIR STRUCTURE FORMATION

Vinyl ether (VE)-based amphiphilic block copolymers with D-glucose residues as hydrophilicpendants were synthesized by CH_3 CH(OiBu)Cl/ZnI_2-initiated sequential living cationic copolymerization of3-O-(vinyloxy)ethyl-1, 2:5, 6-di-O-isopropylidene-D-glucofuranose (IGVE) and isobutyl VE (IBVE ) andsubsequent deprotection. The precursor block copolymers had a narrow molecular weight distribution(M_w/M_n～1.1) and a controlled segmental composition. The solubility characteristics of the amphiphiliccopolymer depended strongly on composition. Their solvent-cast thin films were examined, under atransmission electron microscope, and could be seen to exhibit various microphase-separated surfacemorphologies such as spheres, cylinders, and lamellae, depending on composition. The amphiphiliccopolymers with the appropriate segmental composition were found to form a stable monolayer at the air-water interface, which was successfully transferred onto a substrate by the Langmuir-Blodgett (LB)technique. The layered strucfure of the built-up LB films was controlled by blending the homopolymer.

Alternating Copolymerization of Epoxides and Isothiocyanates to Diverse Functional Polythioimidocarbonates and Related Block Polymers

Synthesis of diverse polythioimidocarbonates via ring-opening copolymerization of epoxides and isothiocyanates catalyzed by organoboron catalyst was reported herein.Both aromatic and aliphatic isothiocyanates underwent successful copolymerization with terminal and internal epoxides,allowing for the precise tuning of the performance of the resultant copolymers over a broad range.The wide scope of available isothiocyanates and epoxides enables the direct construction of sulfur-containing functional polymers featuring both high glass transition temperature and refractive index.Additionally,it was observed that aromatic isothiocyanates polymerize much faster than aliphatic ones,and the reactivity difference facilitated the one-step synthesis of block polymers from mixed aromatic isothiocyanates,aliphatic isothiocyanates and epoxides due to the preferential incorporation of aromatic isothiocyanates over the aliphatic analogues during their alternating copolymerization with epoxides.The produced polythioimidocarbonates can be used as positive resists for electron beam lithography(sensitivity of 130μC/cm^(2) and contrast of 1.53 for poly(CHO-alt-EITC)).Coupling with their high refractive index(1.58—1.68),polythioimidocarbonates might find functional applications in optics.These results render ring-opening copolymerization of epoxides and isothiocyanates a facile route to enrich functional polymer library.

SYNTHESIS AND CHARACTERIZATION OF WELL-DEFINED BLOCK COPOLYMERS CONTAINING PENDANT,SELF-COMPLEMENTARY QUADRUPLE HYDROGEN BONDING SITES

The title block copolymer (defined as PSUEA) containing pendant,self-complementary quadruple hydrogen bonding sites has been prepared successfully by three steps.First,poly(styrene-b-2-hydroxyethyl acrylate) (defined as PSHEA) was prepared by living radical polymerizing 2-hydroxyethyl acrylate (HEA) initiated by polystyrene (PSt) macro- initiator,which was prepared via nitroxide-mediated polymerization (NMP) technique.After treated by excessive 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI),...

Spectroscopic investigation on chirality transfer in additive-driven self-assembly of block polymers

Chiral supramolecules prepared by the additive-driven self-assembly of block copolymers provide a facile method to construct helical nanostructures. In this study, we investigated the chiral transfer from chiral tartaric acid to poly（styrene）-b-poly（ethylene oxide） using small-angle X-ray scattering,transmission electron microscopy, circular dichroism, and vibrational circular dichroism. The results showed that the chirality was transferred to both the segments of block copolymer irrespective of the interaction with the chiral additives and formation of helical phase structure. However, the chirality transfer was carried out using different methods： for poly（ethylene oxide） segments, the chirality transfer was carried out via direct hydrogen bond formation; for polystyrene segments, the chirality transfer was carried out via the cooperative motion of block copolymers during the thermal annealing.

Synthesis and Characterization of the Polyacrylonitrile-block- poly(methyl acrylate) by RAFT Technique

Polyacrylonitrile-block-poly（methyl acrylate）（P（AN-b-MA）） was synthesized by reversible addition-fragmentation chain transfer （RAFT） polymerization employing macro-RAFT agent （PAN-RAFT） as the chain transfer agent and azobis（isobutyronitrile） （AIBN） as the initiator. A linear relationship between ln（[M]0/[M]1） and reaction time was observed. The molecular structure of P（AN-b-MA） was characterized by ^1H-NMR, element analysis, FTIR and SEC. The molecular weight distribution （MWD） was less than 1.40, the Mn could be controled from 0.733 to 4.834×10^4, and the molar content of MA in P（AN-b-MA） were from 15.6 to 75.0 percentage, respectively.

Polyethylene glycol/polylactic acid block co‐polymers as solid–solid phase change materials

Phase change materials(PCMs)are promising thermal energy storage materials due to their high specific latent heat.Conventional PCMs typically exploit the solid–liquid(s–l)transition.However,leakage and leaching are common issues for solid–liquid PCMs,which have to be addressed before usage in practical applications.In contrast,solid–solid(s–s)PCMs would naturally overcome these issues due to their inherent form stability and homogeneity.In this study,we report a new type of s–s PCM based on chemically linked polyethylene glycol(PEG,the PCM portion)with polylactic acid(PLA,the support portion)in the form of a block co‐polymer.Solid‐solid latent heat of up to 56 J/g could be achieved,with melting points of between 44°C and 55°C.For comparison,PEG was physically mixed into a PLA matrix to form a PEG:PLA composite.However,the composite material saw leakage of up to 9%upon heating,with a corresponding loss in thermal storage capacity.In contrast,the mPEG/PLA block co‐polymers were found to be completely homogeneous and thermally stable even when heated above its phase transition temperature,with no observable leakage,demonstrating the superiority of chemical linking strategies in ensuring form stability.

Synthesis of polyacrylonitrile-block-polydimethylsiloxane-block-polyacrylonitrile triblock copolymers via RAFT polymerization

A new A-B-A type of block copolymers,polyacrylonitrile-block-polydimethylsiloxane-block-polyacrylonitrile（PAN-b-PDMSb-PAN）,which comprises two polymer blocks of different polarities and compatibilities,were synthesized for the first time via reversible addition-fragmentation chain transfer polymerization.Reaction kinetics was investigated.PAN-b-PDMS-b-PAN films were prepared by spin-coating on glass chips.Significant order on the film surface morphologies was observed.

Preparation of porous polyimide microspheres by thermal degradation of block copolymers

A new preparation method has been developed for thermally stable porous polyimide microspheres. Porous polyimide microspheres were prepared using trib]ock copolymers that consisted of a thermally stable polyimide derived from pyromellitic dianhydride/4,4＇-oxydianiline as the continuous phase and a thermally labile polyether as the dispersed phase. Spheres of copolymers were generated in a nonaqueous emulsion and then gradually heated to complete the imidization to form a microphase-separated structure. Subsequently, thermal treatment at a slightly reduced pressure removed the labile blocks and produced pores. Under suitable decomposition conditions, the pore size of the porous polyimide was in the range of 200-400nm.

Rational design of phosphonate/quaternary amine block polymer as an high-efficiency antibacterial coating for metallic substrates

Developing advanced technologies to address the bacterial associated infections is an urgent requirement for metallic implants and devices.Here,we report a novel phosphonate/quaternary amine block polymer as the high-efficiency antibacterial coating for metallic substrates.Three pDEMMP-b-pTMAEMA block polymers that bearing identical phosphonate segments(repeat units of 15)but varied cationic segments(repeat units of 8,45,and 70)were precisely prepared.Stable cationic polymer coatings were constructed on TC4 substrates based on the strong covalent binding between phosphonate group and metallic substrate.Robust relationship between the segment chain length of the polymer coating and the antibacterial property endowed to the substrates have been established based on quantitative and qualitative evaluations.Results showed that the antibacterial rate of the modified TC4 surface were 95.8%of S.aureus and 92.9%of E.coli cells attached.Interestingly,unlike the cationic free polymer or cationic hydrogels,the surface anchored cationic polymers do compromise the viability of the attached C2C12 cells but without significant cytotoxicity.In addition,the phosphonate/quate rnary amine block polymers can be easily constructed on titanium,stainless steel,and Ni/Cr alloy with significantly improved antibacterial property,indicating the generality of the block polymer for surface antibacterial modification of bio-metals.

pH-Responsive polymer boosts cytosolic siRNA release for retinal neovascularization therapy

Small interfering RNA(siRNA)has a promising future in the treatment of ocular diseases due to its high efficiency,specificity,and low toxicity in inhibiting the expression of target genes and proteins.However,due to the unique anatomical structure of the eye and various barriers,delivering nucleic acids to the retina remains a significant challenge.In this study,we rationally design PACD,an A-B-C type non-viral vector copolymer composed of a hydrophilic PEG block(A),a siRNA binding block(B)and a pH-responsive block(C).PACDs can self-assemble into nanosized polymeric micelles that compact siRNAs into polyplexes through simple mixing.By evaluating its pH-responsive activity,gene silencing efficiency in retinal cells,intraocular distribution,and anti-angiogenesis therapy in a mouse model of hypoxia-induced angiogenesis,we demonstrate the efficiency and safety of PACD in delivering siRNA in the retina.We are surprised to discover that,the PACD/siRNA polyplexes exhibit remarkable intracellular endosomal escape efficiency,excellent gene silencing,and inhibit retinal angiogenesis.Our study provides design guidance for developing efficient nonviral ocular nucleic acid delivery systems.

Polymerization of lactide and synthesis of block copolymer catalyzed by copper(Ⅱ) Schiff base complex

In the present investigation, the novel copper Schiff base complex was synthesized and its catalytic activity was evaluated for the ring-opening polymerization （ROP） of lactide and block polymerization of poly（lactide） with po/y（ethylene glycol）methyl ether,

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.

Polymeric dual-modal imaging nanoprobe with two-photon aggregation-induced emission for fluorescence imaging and gadolinium-chelation for magnetic resonance imaging

Nanoprobes that offer both fluorescence imaging(FI)and magnetic resonance imaging(MRI)can provide supplementary information and hold synergistic advantages.However,synthesis of such dual-modality imaging probes that simultaneously exhibit tunability of functional groups,high stability,great biocompatibility and desired dual-modality imaging results remains challenging.In this study,we used an amphiphilic block polymer from(ethylene glycol)methyl ether methacrylate(OEGMA)and N-(2-hydroxypropyl)methacrylamide(HPMA)derivatives as a carrier to conjugate a MR contrast agent,Gd-DOTA,and a two-photon fluorophore with an aggregation-induced emission(AIE)effect,TPBP,to construct a MR/two-photon fluorescence dual-modality contrast agent,Gd-DOTA-TPBP.Incorporation of gadolinium in the hydrophilic chain segment of the OEGMA-based carrier resulted in a high r_(1)value for Gd-DOTA-TPBP,revealing a great MR imaging resolution.The contrast agent specifically accumulated in the tumor region,allowing a long enhancement duration for vascular and tumor contrast-enhanced MR imaging.Meanwhile,coupling TPBP with AIE properties to the hydrophobic chain segment of the carrier not only improved its water solubility and reduced its cytotoxicity,but also significantly enhanced its imaging performance in an aqueous phase.Gd-DOTA-TPBP was also demonstrated to act as an excellent fluorescence probe for two-photon-excited bioimaging with higher resolution and greater sensitivity than MRI.Since high-resolution,complementary MRI/FI dual-modal images were acquired at both cellular and tissue levels in tumor-bearing mice after application of Gd-DOTA-TPBP,it has great potential in the early phase of disease diagnosis.

Nanoscale 3D ordered polymer networks

Structures having nanoscale 3 D geometries are valuable as multifunctional materials, where multi-continuous microphases can synergistically influence mechanical, optical, transport and other properties. Such very high interface surface to volume ratio structures occur in a variety of materials including natural materials such as butter fly wings and sea urchin exoskeletons and in synthetic self-assembled structures such as surfactant/water systems and block polymers. Quantitative morphological characterization of such complex geometric structures is quite challenging. Unit cell sizes range from 10–300 nm with corresponding feature sizes on the 2–50 nm scale. Since these nanoscale network structures are bicontinuous, when one constituent is removed, the structure is still self supporting. Removal of one component produces a nanoporous material that may be in-filled with another component, or the surfaces of the nanopores can be coated with ultra-thin layers by atomic layer deposition to offer multifunctional capabilities. Due to the ability to individually tailor the properties of the network(s) and matrix,for example, to create strong dielectric or impedance contrast, such spatially periodic structures are excellent for the interference of waves(electromagnetic for photonic applications and acoustic for phononic applications) that can lead to bandgaps and hence the control of wave propagation in the material. This mini-review will focus on networks formed by bottom up self assembly of block polymers. In addition to structural issues, we emphasize the special physical properties related to bi-or tri-continuous networks.