Macromolecular Chemistry and Physics

In this study a rapid method is developed to obtain Au nanoparticles (AuNPs)/polymer composite materials by which HAuCl₄ salt is reduced and a polymer matrix is simultaneously generated by the means of UV light. 2‐Mercaptothioxanthone (TX‐SH), thioxanthone (TX), and TX + thiophenol are used as photoinitiator system for the poly(ethylene glycol) methyl ether acrylate and poly(ethylene glycol) diacrylate mixtures in the presence of HAuCl₄. Except for a few studies, in situ reduction of Au ions, in an attempt to make them near or at polymer surface, has hardly been investigated at all. As a result of this study, it is important to note that the change of shape of NPs depends on the photoreducing species. TX‐SH, due to thiol functionality in its structure, helps the production of the size, shape, and controlled distribution of AuNPs either in polymer matrix or in solution. Prepared AuNPs/polymer nanocoatings exhibit a reflected gold mirror view depending on the irradiation time. In addition to the foregoing approach in obtaining a thin film in the presence of AuNPs, it is expected that they are well ordered near the film surface with controlled shape and narrow range in size distribution. image

Summary: A series of telechelic OH polysulfones (PSU) were converted to atom transfer radical polymerization (ATRP) macroinitiators by reaction with 2‐bromoisobutyryl bromide. Three macroinitiators with different chain lengths were extended with poly(butyl acrylate) (PBA) to form ABA triblock copolymers. The structure and dynamics of the ABA triblock copolymers with PSU central segments and various molecular weight PBA side chains were investigated by small‐angle X‐ray scattering and rheology. The block copolymers form micelles with a PSU core and PBA corona. The length of each block has an important effect on the structure and resulting dynamics of the copolymers. Dynamic mechanical measurements indicate three relaxation modes: (i) PBA segmental relaxation at high frequency; (ii) PBA relaxation of the corona block at intermediate frequency; (iii) an additional relaxation process related to structural rearrangement of the micelles at low frequency. The shear modulus plateau corresponding to a soft rubbery state extends over a very broad time or temperature range because of this slow additional relaxation.

Schematic illustration of the structural elements and the bulk supramolecular structure for a symmetric triblock copolymer with a stiff central segment strongly incompatible with the other constituent.

Glycidol (2‐epoxy‐1‐propanol) was polymerized under the action of Lewis acids (BF₃OEt_2,, SnCl₄) and protonic acids (CF₃COOH, CF₃SO₃H). Polymers with number‐average molecular weights (M̄_n) varying from 2500 to 6000 g/mol were obtained. The structure of obtained polymers was characterized by ¹³C and ²⁹Si NMR spectroscopy, and the amount of 1‐3 units, 1‐4 units and chain branches was determined. The structure of the polymers was related to the polymerization mechanism, especially to the contribution of activated monomer mechanism in chain growth.

A superhydrophobic textile for biomedical applications is designed using chitosan‐based hydrophobic nanoparticles. The fabrication of nanoparticles is based on the electrostatic interaction between the amine group of chitosan and the negatively charged fluoroanion. The coating is formed by spraying the nanoparticles dispersion over the textile surface, while the complementary hydrophobization by functionalized perfluorodecylsilane leads to substitution of hydrophilic surface groups by hydrophobic ones. The crucial role of the relative number of fluoroanions per elementary unit of chitosan in both surface wettability and durability of coatings in contact with aqueous media is demonstrated. magnified image

Summary: New polyindolocarbazoles (PIC) and polydiindolocarbazoles (PDIC) have been synthesized using Yamamoto polymerization reaction. These polymers have been investigated by cyclic voltammetry, UV‐Vis‐NIR spectroelectrochemistry, electrochemical quartz crystal microbalance, in situ electron spin resonance, and in situ conductivity techniques. Two redox oxidation processes, each involving one electron per repeat unit, produce radical cations (free or π‐dimerized) and dications. Each one‐electron redox process is generally split into two due to the stabilization of mixed‐valence states. The oxidative charge is delocalized over the polyconjugated backbone with neutral‐polaron conductivities in the range 0.002–0.04 S · cm⁻¹ and polaron‐bipolaron conductivities in the range 0.04–0.5 S · cm⁻¹. Conductivities are higher when nitrogen atoms are involved in the conjugation pathway.

Structure of P3IC, P3DIC, P2IC, and P2DIC.

Summary: New alternating copolymers based on indolocarbazole (IC), both two‐ and three‐coupled, and bithiophene (BT) or bis(3,4‐ethylenedioxythiophene) (BiEDOT), were obtained using Stille or Suzuki coupling reactions. Those copolymers have been investigated by cyclic voltammetry, electrochemical quartz crystal microbalance, in situ electron spin resonance, in situ conductivity, and UV‐Vis‐NIR spectroelectrochemistry techniques. All polymer films undergo reversible oxidation processes. One to three isoelectronic oxidation processes, involving one electron per repeat unit, produce radical cations, dications, and radical trications. The oxidative charge is localized in the IC moiety for BT copolymers or over the whole polyconjugated backbone for BiEDOT copolymers. Redox neutral‐polaron conductivities are in the range of 0.02–0.1 S · cm⁻¹ and polaron‐bipolaron conductivities in the range of 0.1–0.7 S · cm⁻¹.

Chemical structure of the PIC derivatives.

With unique physicochemical properties, multiwalled carbon nanotubes (MWCNTs) have enabled major achievement in polymer composites as reinforcing fillers. Nevertheless, high conductivity of raw MWCNTs (R‐MWCNTs) limits their wider applications in certain fields, which require outstanding thermal conductivity, mechanical, and insulation properties simultaneously. In this article, silica (SiO₂) coated MWCNTs core–shell hybrids (SiO₂@MWCNTs) and organically modified montmorillonite (O‐MMT) are employed to modify epoxy (EP) simultaneously. The epoxy‐clay system is cured by using anhydride curing agent. The impact strength and flexural strength of final nanocomposites are greatly improved. Meanwhile, the final composites remain in high electrical insulation. Compared to mixed acid treated MWCNTs (C‐MWCNTs) (0.5 wt%)/EP nanocomposites, the volume resistivity of the O‐MMT(4 wt%)/SiO₂@MWCNTs(0.5 wt%)/EP nanocomposites increases more than six orders of magnitude. Synergistic toughening effect occurs when using core–shell SiO₂@MWCNTs and MMT bifillers. The electrical insulation is attributed to the suppressed electron transport effect by SiO₂layer on the CNTs surface, and the blocked conductive CNTs network by the buried 2D structural O‐MMT. The SiO₂@MWCNTs core–shell hybrids also benefit to decrease the dielectric constant and dielectric loss of CNTs/EP composites. This work provides guidance to using CNTs as reinforcement fillers to toughen the polymers for electric insulating applications.

A series of 3D printable multifunctional ionic gels (IGs) are developed incorporating ionic liquid (IL) in the thiol–ene network of thiol‐based end‐crosslinker and acrylate monomers. The resulted gels, termed as thiol‐ionic gels (T‐IGs), are highly transparent and very soft with IL content of 70–85 wt%. The mechanical and conductive properties of the T‐IGs are found to be largely dependent on the IL content, end‐crosslinker functionalities, and chain‐length of monomers. Progression of ionic conductivity is observed with an increase in IL content and conductivity as high as 5.40 mS cm⁻¹is attained for longer acrylate group containing T‐IGs at room temperature, while further increase is observed at elevated temperature. T‐IGs in all systems are found to exhibit superior thermal stability. Three‐dimensional fabrication of these functional T‐IGs is achieved by optical 3D printing process with microscale resolution in facile steps.

The synthesis of novel triazeno‐group containing photopolymers is described including their characterization by spectroscopic methods, differential scanning calorimetry, and thermogravimetric analysis. Triazene polymers synthesized by a polycondensation reaction between a bisdizaonium salt and a bifunctional secondary amine are well soluble in usual organic solvents. Transparent, light yellow films of these photopolymers may be produced by simple spin‐coating and solution‐casting techniques. The effect of polymer structural elements on the photolytic decomposition is studied. Depending on the structure of the polymer, thermolysis proceeds either via a one‐step or two‐step mechanism.