Highly Efficient and Well‐Controlled Ambient Temperature RAFT Polymerization under Solar Radiation

Highly efficient and well‐controlled ambient temperature reversible addition–fragmentation chain transfer (RAFT) polymerization is readily carried out under environmentally friendly mild solar radiation. This discovery has significantly extended studies from man‐made separated‐spectroscopic‐emission UV‐vis radiation (Macromolecules 2006 , 39, 3770) to natural continuous‐spectroscopic‐emission solar radiation for ambient temperature RAFT polymerization.

     

Supramolecular Dynamics as Origin for Thermally Induced Insoluble‐to‐Soluble‐to‐Insoluble Transitions of Copolymers in Water

The synthesis of cationic mono‐(6‐O‐(1‐vinylimidazolium))‐ß‐cyclodextrin with toluenesulfonate as the corresponding anion is described. Free‐radical copolymerization of the resulting host–guest complex with N‐isopropylacrylamide or N,N‐diethylacrylamide yielded copolymers showing a temperature‐controlled solubility window in water. The impact of different anionic guests and salt concentrations on solubility behavior was investigated via turbidity measurements.

     

Synthesis and Conformation of Three‐Dimensionally Ordered Macroporous Syndiotactic Polystyrene and Poly(p‐methyl styrene)

Three‐dimensionally ordered macroporous (3DOM) syndiotactic polystyrene (sPS) and poly(p‐methyl styrene) (sPPMS) are synthesized using silica colloidal crystal templates with varied diameters in the range of 548–214 nm, and the effect of polymerization space on the conformation of the resulting 3DOM polymers is investigated by spectroscopy and thermal analysis. In‐situ polymerizations of styrene and p‐methyl styrene within the silica templates induce the resulting 3DOM polymers with different conformations and packing of chains, which are different from those of bulk polymers prepared in the absence of templates. Polymerizations in restricted silica templates result in un‐helixication of 3DOM sPS chains and helixication of 3DOM sPPMS chains.

     

One‐Pot Difunctionalization of Poly(ω‐pentadecalactone) with Thiol‐Thiol or Thiol‐Acrylate Groups,Catalyzed by Candida antarctica Lipase B

Summary: An enzymatic one‐pot procedure has been developed for the synthesis of difunctional polyesters containing terminal thiols and acrylates. Candida antarctica lipase B was used as a catalyst for the ring‐opening polymerization of ω‐pentadecalactone. The polymerization was initiated with 6‐mercaptohexanol, then terminated with γ‐thiobutyrolactone or vinyl acrylate to create two types of difunctional polyesters with a very high content of thiol‐thiol or thiol‐acrylate end‐groups.

Difunctionalization of poly‐PDL.     

Direct Observation of Alkyl Chain Interdigitation in Conjugated Polyquarterthiophene Self‐Organized on Graphite Surfaces

A solution processible polymer—poly(3,3‴‐didodecylquaterthiophene) (PQT‐12) is investigated at the liquid/solid interface using the scanning tunneling microscopy (STM). Two‐dimensional ordered films made up of self‐assembled domains, with dimensions of 100 nm × 50 nm adsorbed on highly oriented pyrolytic graphite (HOPG) were formed. These domains consist of parallel lamellar polymer chains, with the alkyl chains forming interdigitated structures, along with U‐shaped and closed ring segments of the polymer chains. A polymer chain packing model is proposed herein, which attempts to propose a correlation between the packing of long chains and charge mobilities. These STM results could help in understanding the relationship between the extended conjugation and molecular organization of the PQT‐12 chains.

     

Monodomain Liquid Crystal Main Chain Elastomers by Photocrosslinking

A new synthetic strategy for the preparation of macroscopically oriented smectic main chain liquid crystal elastomers (MC‐LCE) by the photocrosslinking of laterally functionalized polyesters is presented. X‐ray measurements proved the formation of the monodomain and allowed a quantitative determination of the order parameter. The thermo‐actuation of our material at the phase transition from the liquid‐crystalline to the isotropic phase was demonstrated by temperature dependent measurements of the sample length, showing a fully reversible shape change of ≈40%. Mechanical measurements showed that the sample can be stretched by up to 60% along the smectic layer normal without any reorientation of the structure, in contrast to earlier experiments and theoretical predictions. The results are discussed in the context of limited smectic layer correlation in different types of smectic materials.

     

Formation of o‐Phenylenediamine Oligomers and their Self‐Assembly into One‐Dimensional Structures in Aqueous Medium

Summary: Uniform one‐dimensional (1D) structures of o‐phenylenediamine (oPD) oligomers are obtained by direct mix of AgNO₃ and oPD aqueous solutions at room temperature. The formation of the 1D structures involves two stages: (1) oxidation of oPD by AgNO₃, yielding individual oPD oligomers; and (2) self‐assembly of the oligomers, forming the 1D structures. Upon decreasing medium pH, the 1D structures can break‐apart to form individual oligomers, or vice versa. It is also found that both the concentration and molar ratio of reactants can influence the morphology of the structures thus formed.

Schematic illustration of the formation mechanism of 1D structures from oPD and AgNO₃, and energy‐dispersed spectrum of the precipitate.     

Convenient Method of Chain‐Growth Polycondensation for Well‐Defined Aromatic Polyamides

Summary: For the convenient synthesis of well‐defined poly(N‐octyl‐p‐benzamide)s with low polydispersities, the polycondensation of methyl 4‐octylaminobenzoate ( 1 ) was investigated. Methyl ester monomer 1 polymerized with lithium 1,1,1,3,3,3‐hexamethyldisilazide (LHMDS) in the presence of an initiator in tetrahydrofuran at −10 °C. The highly pure polyamide with a defined molecular weight and a low polydispersity is obtained after simple treatment of the reaction mixture with aqueous NaOH solution, followed by evaporation.

The chain‐growth polycondensation of 4‐octylaminobenzoic acid methyl ester ( 1 ) with lithium 1,1,1,3,3,3‐hexamethyldisilazide (LHMDS) to yield poly(N‐octyl‐p‐benzamide).     

Ring Opening Polymerization of Lactide under Solvent‐Free Conditions Catalyzed by a Chlorotitanium Calix[4]arene Complex

A novel chlorotitanium calix[4]arene complex was synthesized and tested, without activator, as catalyst for the polymerization of L ‐ and rac‐lactide under solvent‐free conditions. The catalyst displayed high activity, which depended on the monomer‐to‐catalyst molar ratio, and led to highly isotactic PLLA. Despite concomitant transesterification during the polymerization, polylactide formation was well‐controlled, the molar mass distribution indexes remaining in the restricted range of 1.2–1.4.

     

Fabrication of Superhydrophobic and Superoleophilic Polystyrene Surfaces by a Facile One‐Step Method

A facile one‐step method has been developed to prepare both superhydrophobic and superoleophilic surfaces of polystyrene (PS) without any chemical modification. A rough film consisting of micro‐bead and nano‐fiber mixed structures is formed by spraying a PS solution onto a large area and any type of substrate. The mixed structures with such unique wettability properties can be used in oil/water separation and as oil sorbents.

     

A Stable and High‐Efficiency Blue‐Light Emitting Terphenyl‐Bridged Ladder Polysiloxane

A novel blue‐light emitting terphenyl‐bridged ladder polysiloxane ( TBLP) was prepared by the condensation of a tetrasilanol monomer via a ladder supramolecular structure. TBLPs emit narrow blue light (420 nm) with high quantum yields (0.96) in diluted solution and shows no evident fluorophore aggregation in the solid state, indicating that the terphenyls are well isolated due to confinement of the ladder‐rungs. In addition, it has excellent emission stability at high temperature based on TGA, DSC and annealing experiments. Overall, TBLPs can be considered as a potential material for fabricating stable and high‐efficiency blue‐light emitting optoelectronic devices.

     

Crosslinkable Vesicles Self‐Assembled by Amphiphilic Hyperbranched Polyester

Summary: Amphiphilic hyperbranched polyester (H20‐AM) with methacrylate end groups was synthesized based on hyperbranched aliphatic polyester (Boltorn™ H20). Narrow‐dispersed crosslinkable vesicles were obtained by dissolving H20‐AM in water, and characterized by laser light scattering and TEM. The hollow structural vesicle is composed of around 350 H20‐AM molecules, having a radius of around 40 nm and of 1.9 × 10⁶ g · mL⁻¹. The vesicles were fixed by crosslinking of methacrylate groups to form shape‐persistent structures.

TEM images of the crosslinked vesicles at lower magnification.     

Nanofibers Self‐assembled from Structural Complementary Borono‐decapeptides

A series of structural complementary decapeptides with phenyl boronic acid tails or borono‐decapeptides (BPs) were designed and synthesized for supramolecular self‐assembly. After dissolving these borono‐decapeptides in deionized (DI) water, well‐defined nanofibers were formed in BP1 (B(OH)₂VEKELVKEKL‐OH) and BP3 (B(OH)₂AELELARARL‐OH). It was found that the self‐assembled borono‐decapeptide BP1 and BP3 have a parallel β‐sheet conformation in the formed nanofibers. The strategy demonstrated here shows a great prospect in preparation of well‐ordered nanofibers via rationally designing the molecular structures of peptides.

     

pH‐Switchable Macroscopic Assembly through Host–Guest Inclusion

A novel pH‐switchable macroscopic assembly is reported using alginate‐based hydrogels functionalized with host (α‐cyclodextrin, αCD) and guest (diethylenetriamine, DETA) moieties. Since the interaction of αCD and DETA is pH sensitive, the host hydrogel and guest hydrogel could adhere together when the pH is 11.5 and separate when the pH is 7.0. Furthermore, this pH‐controlled adhesion and dissociation shows a good reversibility. The host and guest polymers have good biocompatibility; therefore, this pH‐sensitive macroscopic assembly shows great potential in biotechnological and biomedical applications.

     

Redox‐Responsive Hydrogel System Using the Molecular Recognition of β‐Cyclodextrin

Summary: We have successfully constructed a redox‐responsible hydrogel system by combination of β‐cyclodextrin (β‐CD), dodecyl‐modified poly(acrylic acid) [p(AA/C₁₂)], and a redox‐responsive guest, ferrocenecarboxylic acid (FCA). In the reduced state of FCA, the ternary mixture exhibited a gel‐like behavior, whereas, in its oxidized state, the mixture exhibited a sol behavior.

Conceptual illustration for the redox‐responsive hydrogel system.     

Fabrication of a Metal Particle Array Based on a Self‐Assembled Template from a Two‐Armed Polymer

A two‐armed polymer with a crown ether core self‐assembles to produce macroporous films with pores perpendicularly reaching through the film down to the substrate. A possible assembling mechanism is discussed. The pore size can be conveniently adjusted by changing the solution concentration. These through‐hole macroporous films provide a template for fabricating an array of Cu nanoparticle aggregates.

     

Block Copolymer PEO‐b‐PHPMA Synthesis Using Controlled Radical Polymerization on a Chip

Summary: Block copolymers of poly(ethylene oxide‐block‐2‐hydroxypropyl methacrylate) (PEO‐b‐PHPMA) with a range of molecular masses of the PHPMA block were obtained by controlled radical polymerization on a chip (CRP chip) using a PEO macroinitiator. A series of well‐controlled polymerizations were carried out at different pumping rates or reaction times with a constant ratio of monomer to initiator. The stoichiometry of the reactants was also adjusted by varying relative flow rates to change the reactant concentrations.

A schematic of a CRP chip and SEC traces of the PEO‐b‐PHPMA produced from different pump rates with a 1:100 ratio of initiator to monomer. The dashed peaks are the macroinitiator, PEO‐Br (left), and monomer, HPMA (right).     

A Closed‐Loop Phase Diagram in a Weakly Interacting Polyolefin Copolymer Binary Blend System

Summary: The phase behavior of poly(ethylene‐co‐styrene) (PES) and poly(ethylene‐co‐butene) (PEB) blends has been studied. A closed‐loop phase diagram was clearly observed in this weakly interacting system as the styrene content in the PES decreased to about 1 mol‐%. At higher styrene contents, the phase loop starts to interplay with the crystallization transformation at lower temperatures.

Phase diagram of PEB/PES blends. Phase boundary line is only for easy demonstration.     

Preparation of Size Controllable Polypyrrole Sub‐Microcapsules Using SEBS Copolymer as the Building Block

Summary: SEBS is used as building blocks to fabricate size controllable polypyrrole (PPy) capsules. Polypyrrole shells grow on the surfaces of the size controllable oxidant sub‐microparticles dispersed in the solution cast film of a SEBS copolymer by vapor phase polymerization. After washing in ethanol, PPy sub‐microcapsules dispersed in a SEBS matrix are obtained. This technique shows advantages of lower cost and less pollution, as compared with the gold‐template method reported in the literature.

A TEM image of polypyrrole sub‐microcapsules dispersed in a SEBS matrix.     

A Novel Strategy for the Synthesis of Sheet‐Like Polyaniline

Polyaniline (PANI) micro/nanosheets are successfully synthesized by a template‐free method without using any conventional oxidants. Scanning electron microscopy, transmission electron microscopy, and FT‐IR spectroscopy are applied to characterize the products. By investigating the morphologies and chemical structures of the PANI micro/nanosheets, a possible formation mechanism is proposed. In addition, the influences of experimental parameters, such as the kind of dopant, concentration of aniline, and acidity of reaction system, on the morphologies of the PANI micro/nanosheets have been systematically investigated.