Amphiphilic Block‐Graft Copolymers with a Degradable Backbone and Polyethylene Glycol Pendant Chains Prepared via Ring‐Opening Polymerization of a Macromonomer

Well‐defined amphiphilic block‐graft copolymers PCL‐b‐[DTC‐co‐(MTC‐mPEG)] with polyethylene glycol methyl ether pendant chains were designed and synthesized. First, monohydroxyl‐terminated macroinitiators PCL‐OH were prepared. Then, ring‐opening copolymerization of 2,2‐dimethyltrimethylene carbonate (DTC) and cyclic carbonate‐terminated PEG (MTC‐mPEG) macromonomer was carried out in the presence of the macroinitiator in bulk to give the target copolymers. All the polymers were characterized by ¹H NMR and gel permeation chromatography (GPC). The polymers have unimodal molecular weight distributions and moderate polydispersity indexes. The amphiphilic block‐graft copolymers self‐assemble in water forming stable micelle solutions with a narrow size distribution.

     

Enhancement of Electrochromic Contrast by Tethering Conjugated Polymer Chains onto Polyhedral Oligomeric Silsesquioxane Nanocages

Copolymerization of aniline with octa(aminophenyl) silsesquioxane (OAPS) was performed, which resulted in polyaniline‐tethered, polyhedral oligomeric silsesquioxane (POSS‐PANI), with star‐like molecular geometry. The spectro‐electrochemical studies show that the electrochromic contrast of POSS‐PANI is much higher than that of polyaniline (PANI). The great improvement can be attributed to the more accessible doping sites and the facile ion movement during the redox switching, brought by the loose packing of the PANI chains. This was evidenced by a drastic increase in ionic conductivity, a decrease in the electrical conductivity, and a decrease in the crystallinity and crystal size, with the increase of the OAPS concentration in the POSS‐PANI.

     

Synthesis and Properties of Oligophenylene‐Layered Polymers

We report syntheses of phenylene‐, biphenylene‐, and terphenylene‐layered polymers with a xanthene scaffold by the modified Suzuki‐Miyaura coupling reaction. Their optical properties were studied in detail. The polymer end‐capped by nitrobenzene units, which act as fluorescence quenchers, exhibited the photo‐excited energy transfer from the layered oligophenylenes to the terminal units.

     

Synthesis of Biotinylated Aldehyde Polymers for Biomolecule Conjugation

Biotinylated polymers with side‐chain aldehydes were prepared for use as multifunctional scaffolds. Two different biotin‐containing chain transfer agents (CTAs) and an aldehyde‐containing monomer, 6‐oxohexyl acrylate (6OHA), are synthesized. Poly(ethylene glycol) methyl ether acrylate (PEGA) and 6OHA are copolymerized by reversible addition‐fragmentation chain transfer (RAFT) polymerization in the presence of the biotinylated CTAs. The resulting polymers are analyzed by GPC and¹H NMR spectroscopy. The polymer end groups contained a disulfide bond, which could be readily reduced in solution to remove the biotin. Reactivity of the aldehyde side chains is demonstrated by oxime and hydrazone formation at the polymer side chains, and conjugate formation of fluorescently labeled polymers with streptavidin is investigated by gel electrophoresis.

     

Wettability of Polyhedral Oligomeric Silsesquioxane Nanostructured Polymer Surfaces

Summary: Some model structures of waterborne polyurethane anionomers containing various amounts (ca. 3–20%) of a diol functionalized polyhedral oligomeric silsesquioxane (POSS) nanofiller were prepared. X‐ray diffraction showed the formation of a nanocrystalline structure in all copolymers considered. Static contact angle measurements indicated a significant enhancement of surface hydrophobicity as well as reduction in surface tension components even at the least POSS level (3%). Dynamic contact angle cycles allowed the evaluation of the hysteresis, which was found to be large and kinetically increasing in POSS‐modified samples. Film topography was analyzed by AFM, showing a more pronounced roughness in the nanostructured surface.

The AFM image showing a moderate roughness increase.     

Multi‐Morphological Complex Aggregates Formed from Amphiphilic Poly(ethylene oxide)‐block‐Polydimethylsiloxane‐block‐Poly(ethylene oxide) Triblock Copolymers

Summary: Amphiphilic triblock copolymers (PEO_x‐b‐PDMS_y‐b‐PEO_x) with different block lengths were synthesized and multi‐morphological complex crew‐cut, star‐like, and short‐chain aggregates were prepared by self‐assembly of the given copolymers. The morphologies and dimensions of the aggregates can be well controlled by variation of the preparation conditions. TEM, SEM, FFR‐TEM, and LLS studies show the resulting morphologies range from LCMs, unilamellar or multilayer vesicles, LCVs, porous spheres to nanorods.

TEM images of the vesicles formed from PEO‐b‐PDMS‐b‐PEO.     

Self‐supporting Polymer from a POSS Derivative

A new polyhedral oligomeric silsesquioxane macromer, octakis[N‐(6‐aminopyridin‐2‐yl)undecanamide‐10‐dimethyl‐siloxy]silsesquioxane (POSS‐C11‐Py), containing eight diaminopyridine arms, is able to self‐assemble to form a physically crosslinked polymer‐like structure with good mechanical properties (tensile strength = 46.1 MPa, tensile modulus = 0.58 GPa, elongation = 49.3%) through quadruple hydrogen bonding interactions between these arms. POSS‐C11‐Py is the first organic/inorganic supermolecule possessing polymer‐like mechanical properties as a result of self‐complementary interactions, providing a potential route toward the design and fabrication of polymer‐like supramolecular materials.

     

Amphiphilic Hybrid π‐Conjugated Polymers Containing Polyhedral Oligomeric Silsesquioxanes

Amphiphilic hybrid π‐conjugated polymers that have polyhedral oligomeric silsesquioxanes on their side chains have been successfully synthesized by the Sonogashira–Hagihara polycondensation reaction. The obtained polymers were studied with ultraviolet‐visible absorption and photoluminescence spectra. In these polymers, the π‐conjugation length was extended along the poly(p‐phenylene‐ethynylene) backbone. Furthermore, the content of the POSS substituents can influence the aggregation behavior of the polymers and subsequent luminescent properties.

     

Precise Block‐Copolymers by Efficient Coupling of End‐Functionalized Polymers Using Phosgene

Summary: We report the synthesis of well‐defined block copolymers by covalent coupling of hydroxy end‐functionalized polymers. Using the high volatility of the coupling agent phosgene as compared to the solvent, very high conversion (up to 96%) is obtained in a one‐pot reaction with as little as 10⁻⁵ moles of each of the reacting polymers, even without prior purification of the as‐received reagents. This has potential as an alternative to the currently practiced method of sequential living polymerization of constituent monomers, with the added advantage of direct knowledge and control over the length distribution of each block.

Coupling of end‐functionalized polymers using phosgene to form block copolymers of controlled composition.     

1,1‐Diphenyl Ethylene‐Mediated Radical Polymerisation: A General Non‐Metal‐Based Technique For The Synthesis Of Precise Core Cross‐Linked Star Polymers

This communication details the successful synthesis of low polydispersity core cross‐linked star (CCS) polymers via DPE‐mediated polymerisation. We demonstrate the ability to produce poly(methyl methacrylate) and poly(acrylonitrile) CCS polymers that are currently inaccessible via the two most common non‐metal‐based controlled radical polymerisation techniques (NMP and RAFT polymerisations).

     

Proton Conducting Polysulfone Ionomers Carrying Sulfoaryloxybenzoyl Side Chains

Summary: Novel proton conducting ionomers have been prepared by attaching pendant sulfonated aromatic side chains to polysulfone. Lithiated polysulfone was first reacted with 4‐fluorobenzoic acid chloride to introduce 4‐fluorobenzoyl side chains to the polymer main chain. Next, the activated fluoro groups were replaced by 4‐sulfophenoxy or 7‐sulfo‐2‐naphthoxy in a potassium carbonate‐mediated nucleophilic substitution reaction. This reaction proceeded under full conversion and the degree of substitution was easily controlled by the degree of lithiation in the first step. Membranes based on ionomers carrying one sulfophenoxybenzoyl unit per polymer repeat unit reached a proton conductivity exceeding 30 mS · cm⁻¹ at 120 °C under immersed conditions.

Structures of sulfophenoxybenzoyl polysulfone and sulfonaphthoxybenzoyl polysulfone.     

Preparation of Clickable Poly(3‐hydroxyalkanoate) (PHA): Application to Poly(ethylene glycol) (PEG) Graft Copolymers Synthesis

A new synthesis of amphiphilic biodegradable copolymers consisting of hydrophobic poly(3‐hydroxyalkanoate) (PHA) backbone and hydrophilic poly(ethylene glycol) (PEG) units as side chains is described. Poly[(3‐hydroxyoctanoate)‐co‐(3‐hydroxyundecenoate)] (PHOU) was first methanolyzed and its unsaturated side chains were quantitatively oxidized to carboxylic acid. Esterification with propargyl alcohol led to an alkyne‐containing “clickable” PHA in 71% conversion. Its reactivity was successfully demonstrated by grafting azide‐terminated PEG chains of 550 and 5 000 g · mol⁻¹, respectively. All products were fully characterized using GPC, ¹H, and COSY NMR.

     

Effect of Free Trimethylaluminum Content in Methylaluminoxane on Performances of Bis(salicylaldiminate)nickel(II)‐Based Catalysts for Ethylene Polymerization

Summary: The performances of ethylene polymerization catalysts based on III and commercial methylaluminoxane were investigated by reducing the content of free trimethylaluminum in methylaluminoxane by its reaction with 2,6‐di‐tert‐butylphenol. This allowed optimization of the formulation of the catalyst, affording a high‐molecular‐weight linear polyethylene (PE) with a productivity [(1 900 kg of PE/(mol of Ni × h)], ten‐fold higher than that previously achieved for the same system adopting commercial methylaluminoxane not pre‐treated with the above phenol derivative.

     

A Versatile Preparation Route for Thin Free‐Standing Liquid Single Crystal Elastomers

Summary: Thin films of nematic and cholesteric side‐chain polymers containing reactive benzophenone units can be macroscopically oriented by electric/magnetic fields or surface interactions. After UV‐irradiation, liquid single crystal elastomers (LSCEs) are formed. With this simple, new pathway, macroscopically ordered free‐standing LSCE films are easily accessible having a thickness in the range of about 100 nm to 100 μm as outlined in Figure.

     

Synthesis of POSS‐Functionalized Polyisobutylene via Direct Initiation

POSS‐functionalized polyisobutylenes (PIBs) were synthesized by carbocationic polymerization using an epoxy‐POSS/TiCl₄ initiating system in hexane/methyl chloride (60:40 v/v) solvent mixture at −80 °C. ¹H NMR spectroscopy verified the incorporation of one epoxy‐POSS per polymer chain. Light scattering and TEM analysis demonstrated the formation of 50–100 nm sized aggregates and micron‐sized clusters.

     

The Self‐Assembled Structure of the Diblock Copolymer PCL‐b‐P4VP Transforms Upon Competitive Interactions with Octaphenol Polyhedral Oligomeric Silsesquioxane

This paper describes the miscibility and self‐assembly, mediated by hydrogen‐bonding interactions, of new block copolymer/nanoparticle blends. The morphologies adopted by the immiscible poly[(ε‐caprolactone)‐block‐(4‐vinyl pyridine)] (PCL‐b‐P4VP) diblock copolymer changes upon increasing the number of competitive hydrogen‐bonding interactions after adding increasing amounts of octaphenol polyhedral oligomeric silsesquioxane (OP‐POSS). Transmission electron microscopy reveals morphologies that exhibit high degrees of long‐range order, such as cylindrical and spherical structures, at relatively low OP‐POSS contents, and short‐range order or disordered structures at higher OP‐POSS contents. Analyses performed using differential scanning calorimetry, wide‐angle X‐ray diffraction, and FT‐IR spectroscopy provide positive evidence that the pyridyl units of the P4VP block are significantly stronger hydrogen‐bond acceptors toward the OH group of OP‐POSS than are the CO groups of the PCL block, thereby resulting in excluded and confined PCL phases.

     

New π‐Conjugated Polymers Containing 1,3,5‐Triazine Units in the Main Chain: Synthesis and Optical and Electrochemical Properties of the Polymers

Summary: Three new soluble π‐conjugated polymers containing 1,3,5‐triazine units in the main chain, Pa–Pc, were synthesized. The polymers showed optical properties in solution that were mainly dependant on the properties of the substituting R groups, on the triazine ring. Hence, Pa and Pb (R = H and  OCH₃, respectively) showed blue photoluminescent (PL) emission with high quantum yields (QY) even in polar solvents, whereas Pc (R = N,N‐dimethylamino) gave green‐blue PL emission with very low QY. The PL spectra of the polymers in solution were concentration and polarity dependent, which suggested the formation of an exciplex.

The three new soluble π‐conjugated polymers containing 1,3,5‐triazine units in the main chain synthesized here.     

A Triphenylamine‐Based Conjugated Polymer with Donor‐π‐Acceptor Architecture as Organic Sensitizer for Dye‐Sensitized Solar Cells

A conjugated polymer containing an electron donating backbone (triphenylamine) and an electron accepting side chain (cyanoacetic acid) with conjugated thiophene units as the linkers has been synthesized. Dye‐sensitized solar cells (DSSCs) are fabricated utilizing this material as the dye sensitizer, resulting a typical power conversion efficiency of 3.39% under AM 1.5 G illumination, which represents the highest efficiency for polymer dye‐sensitized DSSCs reported so far. The results show the good promise of conjugated polymers as sensitizers for DSSC applications.

     

Polyhedral Oligomeric Silsesquioxane Containing Copolymers for Negative‐Type Photoresists

Summary: A series of methacrylate copolymers containing polyhedral oligomeric silsesquioxane (POSS) was synthesized from the free radical copolymerization of methacrylic acid, methyl methacrylate, and isobutyl propylmethacryl polyhedral oligosilsesquioxanes, and then were modified with glycidyl methacrylate to serve as negative‐type photoresists. The UV/Vis spectroscopy reveals that the incorporation of POSS moiety into the copolymer results in a slight decrease in transparency from 99 to 92.5% (at wavelength = 365 nm). The photosensitivity in terms of resist sensitivity (D), contrast (γ), and photopolymerization rate are significantly increased with increase in the POSS content. In addition, the induction time is reduced from 0.520 to 0.515 min after incorporating the POSS unit based on photo‐DSC analyses. These observed results can be rationalized as due to hydrogen bonding interactions between siloxane and hydroxyl groups in copolymers which tend to attract the methacrylate double bonds surrounding POSS units to crosslink, thereby enhancing the photopolymerization rate and sensitivity. We further evaluate the lithographic property of a photoresist under a collimated exposure.

Compact double bonds zone induced via hydrogen bonding.     

Simultaneous Preparation of PI/POSS Semi‐IPN Nanocomposites

Summary: This investigation presents a simultaneous and convenient approach to produce a high‐performance polyimide with a low dielectric constant by introducing the octa‐acrylated polyhedral oligomeric silsesquioxane (methacrylated‐POSS) into a polyimide matrix to form polyimide semi‐interpenetrating polymer network (semi‐IPN) nanocomposites. The differential scanning calorimetry (DSC) and Fourier‐transform infrared (FT‐IR) results indicate that the self‐curing of methacrylated‐POSS and the imidization of polyamic acid (PAA) occurs simultaneously. The morphology of a semi‐IPN structure of polyimide/POSS‐PI/POSS nanocomposites with POSS nanoparticles embedded inside the matrix is elucidated. The POSS particles are uniform and are aggregated to a size of approximately 50–60 nm inside the polyimide matrix. The interconnected POSS particles are observed at high POSS content. The structure is highly cross‐linked, so the PI/POSS nanocomposites have an enhanced glass transition temperature. The high porosity of the PI/POSS nanocomposites markedly reduces the dielectric constant of PI because of the nanometer‐scale porous structure of POSS.

FT‐IR spectra of the various compounds of A) methacrylate‐POSS before curing, B) methacrylate‐POSS after curing, C) PAA containing 15 wt.‐% POSS, and D) PI/POSS containing 15 wt.‐% POSS.