Tailoring of Co‐Continuous Polymer Blend Morphology: Joint Action of Nanoclays and Compatibilizers

The effect of both organoclay (Cloisite® 30B) and compatibilizers (EVA copolymer or MAgPE) on the morphology and mechanical properties is investigated with a special focus on co‐continuous structures. For that purpose, LDPE and PBAT are selected as an inert/reactive polymer pair model. The influence of the nature of the nanoclay/compatibilizer pair on the morphology of the nanocomposite is studied by means of SEM and TEM. Depending on the compatibilizer, it comes out that the organoclay can be selectively located in either the polyolefinic or polyester phase while the interface is invariably stabilized by clay platelets. Interestingly enough, it appears that such a combination (organoclay plus compatibilizer) allows for tailoring the final properties of polymer blends.

     

Double‐Gyroid Morphology of a Polystyrene‐block‐Poly(ferrocenylethylmethylsilane) Diblock Copolymer: A Route to Ordered Bicontinuous Nanoscale Architectures

A polystyrene‐block‐poly(ferrocenylethylmethylsilane) diblock copolymer, displaying a double‐gyroid morphology when self‐assembled in the solid state, has been prepared with a PFEMS volume fraction ?_PFEMS = 0.39 and a total molecular weight of 64 000 Da by sequential living anionic polymerisation. A block copolymer with a metal‐containing block with iron and silicon in the main chain was selected due to its plasma etch resistance compared to the organic block. Self‐assembly of the diblock copolymer in the bulk showed a stable, double‐gyroid morphology as characterised by TEM. SAXS confirmed that the structure belonged to the Ia d space group.

     

Self‐Assembly of a Hydrogen‐Bonded Association Chain Liquid Crystalline Polymer (LCP)

A hydrogen‐bonded association chain liquid crystalline polymer (LCP) based on tetraethyleneglycoxy‐bis(2,6‐dimethyl‐4‐benzoic acid) and 4,4′‐(p‐phenylenedi‐1,2‐ethenediyl)bipyridyl in a 1 : 1 stoichiometric ratio was synthesized using melting mixing method. X‐ray scattering from fiber drawn from its nematic phase exhibits preferred orientation, indicating that hydrogen bonding association chain polymer can also be strong enough to withstand the shear or tensile force and could be macroscopically oriented under shear or tensile force. Two complimentary components are likely to form a co‐crystallized structure to form a monoclinic crystal.     

Temperature and pH Controlled Self‐Assembly of a Protein–Polymer Biohybrid

A novel pH and temperature dual‐responsive bioconjugate is prepared by grafting thermoresponsive polymer chains from a pH‐responsive protein amelogenin via atom transfer radical polymerization. To the best of our knowledge, this is the first time that amelogenin is exploited to prepare a hybrid biomaterial with new stimuli‐responsive property. In both basic and acidic solutions the protein–polymer bioconjugate is able to self‐assemble into uniform and stable nanoparticles when heated to above the lower critical solution temperature of the polymer. The amelogenin‐based stimuli‐responsive bioconjugate may be of great use in the fields of bioseparation and drug/gene delivery, and the synthetic approach reported here should provide a convenient means to preparing amelogenin‐based functional biohybrid materials.     

Synthesis and Self‐Assembly of o‐Nitrobenzyl‐Based Amphiphilic Hybrid Polymer with Light and pH Dual Response

In this paper, novel light‐responsive polyhedral oligomeric silsesquioxane (POSS) end‐capped poly(o‐nitrobenzyl methacrylate) (POSS–PNBMA) are synthesized by the combination of atom transfer radical polymerization (ATRP) and click chemistry. After subsequent partial photocleavage of PNBMA yielding poly(methacrylic acid) (PMAA), pH‐ and light‐responsive random copolymer of POSS–P(NBMA‐co‐MAA) is obtained. The o‐nitrobenzyl‐based amphiphilic hybrid polymer can self‐assemble into spherical micelles in aqueous solution. Hydrophobic POSS and PNBMA segments aggregate into the inner core, and the hydrophilic PMAA chains tend to stretch from the core. The micellar morphology can be tuned by pH changes and UV irradiation. Light irradiation leads to the transformation of P(NBMA‐co‐MAA) into PMAA and to the reorganization of the assemblies, causing the release of encapsulated guest molecule Nile Red into water. This dual‐responsive polymer has a broad potential use in targeted drug delivery.

     

Two‐Dimensional Marangoni‐Instability‐Induced Periodic Patterns of Polymer Blend Films Cast on Tilted Substrates

Two‐dimensional periodic patterns were observed for PS/PVP blend films and the corresponding homopolymer films on tilted glass substrates. They were attributed to the Marangoni instability resulting from surface tension non‐uniformity. For the 1:1 PS‐1/PVP‐1 blend films, two‐dimensional regular arrays of the separated phases were observed, similar to those observed on homopolymer films from thickness variations. In addition, for the PS‐2/PVP‐2 blend films of 30/70 composition, one‐dimensional strip patterns of separated phases were observed. The pattern formation mechanism is discussed and a characteristic parameter, defined as the ratio of the final film thickness to initial solution viscosity, is found to correlate well with the pattern regularity through variation in polymer concentration.

     

On the Nature of the Breath Figures Self‐Assembly in Evaporated Polymer Solutions: Revisiting Physical Factors Governing the Patterning

The breath‐figures self‐assembly process was studied. Polystyrene and polycarbonate were dissolved in a diversity of solvents including, acetone, dichloromethane, chloroform, carbon tetrachloride, tetrahydrofuran, toluene, xylenes, carbon disulfide, and N‐N dimethylformamide, and then were evaporated in a humid atmosphere. It was demonstrated that all solutions when sufficiently pre‐cooled gave rise to typical “breath‐figures” patterns. Thus, the decisive factor affecting the formation of the breath‐figures pattern is the temperature of the solution. Wetting properties of the manufactured patterns are reported.     

Thermoresponsive Interpolymeric Complex Assemblies from Co‐association of Linear PAAc Homopolymers with PNIPAAm Segments Containing PAAc‐Based Graft Copolymer

In aqueous solution at pH 3.0 and 20 °C, poly(acrylic acid)‐g‐poly(N‐isopropylacrylamide)/monomethoxy poly(ethylene glycol) (PAAc‐g‐PNIPAAm/mPEG) can assemble spontaneously with linear poly(acrylic acid) homopolymers (homoPAAc) into interpolymeric complexes (IPC). The resultant IPC assemblies exhibit a core–corona structure consisting of a hydrophobic PAAc/PNIPAAm complex core surrounded by hydrated PNIPAAm/mPEG coronas. At temperatures above 30 °C, the assemblies transform into a core–shell–corona micelle. Highly loose, irregular IPC assemblies developed at a reduced weight ratio of homoPAAc with the graft copolymer at 20 °C show particle size enlargement and structural variation above 30 °C. By contrast, co‐assembly of long homoPAAc chains with the copolymer leads to large aggregates comprising several IPC assemblies interconnected by homoPAAc chain segments.

     

Enhancement of the Molecular Ordering via the Polymerization of 3,4‐Ethylenedioxythiophene‐Based Two‐Monomer‐Connected Precursor with 4,4‐Biphenyldisulfonic Acid

The polymerization of 3,4‐ethylenedioxythiophene (EDOT)‐based two‐monomer‐connected precursors in various solvent systems leads to improved crystallinity, compared to poly(3,4‐ethylenedioxythiophene) synthesized from traditional route. The P(EDOT:BPDSA:EDOT) is ordered by using 4,4‐biphenyldisulfonic acid (BPDSA) that is a connector and dopant linking EDOT monomers. The crystallinity, measured from X‐ray diffraction studies, is increased when using short chain or hydrophobic solvents. The crystallinity of P(EDOT:BPDSA:EDOT) significantly increases up to 45.0% compared to polymer with other sulfonic acids, bifunctional 1,2‐ethanesulfonic acid, and monofunctional methanesulfonic acid (MSA). The crystal structure is also confirmed from high‐voltage electron microscope. From these studies, it is confirmed that P(EDOT:BPDSA:EDOT) has an orthorhombic structure, which has the unit cell lattice parameters of a = 1.44 nm, b = 0.98 nm, and c = 1.18 nm from fast Fourier transform pattern images. The electrical conductivity is increased about four times with BPDSA (0.21 S cm^?1) when compared using MSA (0.06 S cm^?1).     

Controlled ROMP Synthesis of Ferrocene‐Containing Amphiphilic Dendronized Diblock Copolymers as Redox‐Controlled Polymer Carriers

Novel well‐defined redox‐responsive Ferrocene (Fc)‐containing amphiphilic dendronized diblock copolymers are synthesized by the ring‐opening metathesis polymerization technique using Grubbs’ third‐generation olefin metathesis catalyst as the initiator. These dendronized block copolymers can self‐assemble into spherical micelles in aqueous solution. The size of self‐assembled micelles can be modulated by the composition (namely, the ratio of hydrophobic and hydrophilic segments) and concentration of the dendronized copolymers. The obtained micelles show reversible redox‐controlled self‐assembly behaviors using FeCl₃ as oxidant and glutathione as reductant. Furthermore, the model molecule Rhodamine B is successfully loaded in these micelles, and the oxidation‐triggered controllable release is achieved by changing the type of oxidants (FeCl₃ and H₂O₂) and their concentrations. This is the first example of redox‐responsive micelles self‐assembled by novel amphiphilic dendronized Fc‐containing block copolymers, and the present micelles are visualized to be potential candidates in many fields, especially in stimuli‐responsive drug delivery systems.     

Targeted Droplet‐Digital PCR as a Tool for Novel Deletion Discovery at the DFNB1 Locus

Pathogenic variants at the DFNB1 locus encompassing the GJB2 and GJB6 genes account for 50% of autosomal‐recessive, congenital nonsyndromic hearing loss in the United States. Most cases are caused by sequence variants within the GJB2 gene, but a significant number of DFNB1 patients carry a large deletion (GJB6‐D13S1830) in trans with a GJB2 variant. This deletion lies upstream of GJB2 and was shown to reduce GJB2 expression by disrupting unidentified regulatory elements. First‐tier genetic testing for hearing loss includes GJB2 sequence and GJB6‐D13S1830 deletion analysis; however, several other deletions in this locus, each with distinct breakpoints, have been reported in DFNB1 patients and are missed by current panels. Here, we report the development of a targeted droplet digital polymerase chain reaction‐based assay for comprehensive copy‐number analysis at the DFNB1 locus that detects all deletions reported to date. This assay increased detection rates in a multiethnic cohort of 87 hearing loss patients with only one identified pathogenic GJB2 variant. We identify two deletions, one of which is novel, in two patients (2/87 or 2.3%), suggesting that other pathogenic deletions at the DFNB1 locus may be missed. Mapping the assayed DFNB1 deletions also revealed a ～95 kb critical region, which may harbor the GJB2 regulatory element(s).     

Directing the Self‐Assembly of Mesostructured Hybrid Materials: Effect of Polymer Concentration and Solvent Type

Herein we explore the possibility to control the fabrication of non‐equilibrium nano‐patterns of spin‐coated organic‐inorganic hybrid materials based on diblock copolymers and metal nanoparticles in thin films. It is demonstrated that the type of solvent and the initial solution concentration, among other factors, can serve as tools to direct the morphology of spin‐coated thin films. The driving forces leading to the pattern formation are reviewed with respect to these parameters—type of solvents and polymer concentration. As a result well‐defined surface patterns of functional hybrid materials are obtained. Moreover, the same tools used to direct the pattern formation can be applied to gain control over the particle size and size distribution.

     

Co‐continuous Nanostructured Blend by Reactive Blending: Incorporation of High Molecular Weight Polymers

One of the most challenging issues remaining in the design and the synthesis of robust nanostructured polymers blends is incorporating long crystallizable chains while preserving the co‐continuity of the phases. Here, we demonstrate that by reactive blending of functionalized polyolefin and polyamides such co‐continuous structures can be obtained provided that a bimodal mixture of short and long polyamides is used. The short chains react more readily to form graft copolymers that facilitate both grafting of long chains and formation of nanostructures. We discuss different mixing strategies, characterize, and compare reacted products and resulting blend structures.

     

Polymer Loops vs. Brushes on Surfaces: Adsorption,Kinetics, and Viscoelastic Behavior of α,ω‐Thiol Telechelics on Gold

Telechelic thiopolymers were explored towards formation of doubly‐bound (polymer loops) vs. singly‐bound (polymer brushes) chains on gold substrates. The conformation, adsorption kinetics, and viscoelastic properties of the α,ω‐dithiol and monothiol PS telechelics were investigated by means of XPS and QCM‐D techniques. The oxidation behavior of the free thiol proved to be important for distinguishing doubly‐bound vs. singly‐bound chains. The results show a critical dependence of $\overline {M} _{{\rm n}} $ on the ability to obtain polymer loops. Comparison with unperturbed dimensions obtained by scaling theory show that the loop is less stretched and occupies more lateral space than the brush. The results are important in demonstrating the different and perhaps superior properties of polymer loops vs. singly‐bound polymer brushes.

     

Hydrogen‐Bonded Shape‐Persistent Aryl Hydrazide Polymers: Side‐Chain‐Tuned Formation of Vesicles and Organogels

A new class of aromatic, hydrazide‐based, zigzag polymer has been synthesized using the Yamazaki polymerization conditions. Hydrophobic, hydrophilic or amphiphilic side chains are introduced to the backbones to tune their solubility in organic solvents of different polarities. The side chains form successive, intramolecular, six‐membered RO···HN hydrogen bonds, which increase the planarity of the backbones. The new shape‐persistent polymers are revealed to self‐assemble into vesicles or fibers to gelate organic solvents of different polarities. The polymeric backbones may be regarded as a conceptual extension of the emerging foldamers, which are usually constructed from oligomeric backbones.

     

Counterion‐Mediated Self‐Assembly of Ion‐Containing Block Copolymers on the Basis of the Hofmeister Series

A Cl^? and I^? ion‐containing amphiphilic diblock copolymer [PEO‐b‐P(qVBC‐co‐St)], IBCP , which comprises the poly(ethylene oxide) block and poly(quaternized 4‐vinylbenzyl chloride‐co‐styrene) is prepared by sequence reactions. Then the counterion‐mediated self‐assembly behavior in aqueous solution is investigated in detail. The hydrophilicity of anion containing units (qVBC) is controlled by the nature of the different counterions after ion exchange, which is crucial in regulating the self‐assembly process. The addition of Br^?, I^?, and SCN^? counterions (based on the Hofmeister series) results in the formation of tighter ion‐pairs with cations (i.e., more hydrophobic as the qVBC units), which triggers spheres to vesicles, micro‐meter long cylinders and “branched wormlike” aggregates, respectively. Moreover, addition of different amounts of Cl^? also causes morphological transition from spheres to long cylinders. And this morphological transition is totally reversible after removing additional Cl^?. The adhesive collisions of spherical particles may contribute to the observed sphere‐to‐cylinder morphological transition.     

Transforming the Self‐Assembled Structures of Diblock Copolymer/POSS Nanoparticle Composites Through Complementary Multiple Hydrogen Bonding Interactions

Well‐defined self‐assembled structures are obtained in the form of block copolymer (BCP) nanocomposites, prepared by blending octuply adenine (A)‐functionalized polyhedral oligomeric silsesquioxane (OBA‐POSS) nanoparticles (NPs) with a thymine (T)‐containing BCP (PS‐b‐PVBT); these nanocomposites are stabilized through complementary multiple hydrogen bonding interactions between the A and T units. A transition from one ordered morphology to another occurs upon increasing the content of OBA‐POSS NPs in the PS‐b‐PVBT diblock copolymer, namely lamellar structures at relatively low OBA‐POSS NP contents (<25 wt%) and cylindrical structures at higher OBA‐POSS NP contents (>25 wt%), with concomitant variations in the effective interaction parameter and the overall volume fractions of the two microphase‐separated domains.

     

Fiber‐Like Micelles from the Crystallization‐Driven Self‐Assembly of Poly(3‐heptylselenophene)‐block‐Polystyrene

The crystallization‐driven self‐assembly (CDSA) of crystalline‐coil polyselenophene diblock copolymers represents a facile approach to nanofibers with distinct optoelectronic properties relative to those of their polythiophene analogs. The synthesis of an asymmetric diblock copolymer with a crystallizable, π‐conjugated poly(3‐heptylselenophene) (P3C7Se) block and an amorphous polystyrene (PS) coblock is described. CDSA was performed in solvents selective for the PS block. Based on transmission electron microscopy (TEM) analysis, P3C7Se₁₈‐b‐PS₁₂₅ formed very long (up to 5 μm), highly aggregated nanofibers in n‐butyl acetate (nBuOAc) whereas shorter (ca. 500 nm) micelles of low polydispersity were obtained in cyclohexane. The micelle core widths in both solvents determined from TEM analysis (≈ 8 nm) were commensurate with fully‐extended P3C7Se₁₈ chains (estimated length = 7.1 nm). Atomic force microscopy (AFM) analysis provided characterization of the micelle cross‐section including the PS corona (overall micelle width ≈ 60 nm). The crystallinity of the micelle cores was probed by UV–vis and photoluminescence (PL) spectroscopy and wide‐angle X‐ray scattering (WAXS).     

Post‐Assembly of Oxidation‐Responsive Amphiphilic Triblock Polymer Containing a Single Diselenide

Linear amphiphilic triblock polymers containing a single diselenide (SeSe‐tri‐ABP) are synthesized by coupling reactions. They self‐assemble into spherical micelles 1 in aqueous solution. A remarkable morphology transformation of the micelles is confirmed through dynamic light scattering (DLS) and transmission electron microscopy (TEM). The release behavior of a model molecule, Rhodamine B (RB), is studied by UV–vis spectrophotometry. It is found that post‐assembly from micelles 1 to micelles 2 is induced by the oxidation‐responsive cleavage of the diselenide group in the oxidation solution. Interestingly, the RB release studies reveal that these micelles release RB in a diphasic pattern (slow after initial fast release) within 24 h under an oxidative environment. In contrast, minimal drug release (<20%) is observed within 24 h for SeSe‐tri‐ABP micelles under aqueous conditions. Meanwhile, this release behavior of the RB‐loaded micelles can be tuned by the post‐assembly of oxidation‐responsive SeSe‐tri‐ABP in different oxidation conditions, providing a promising platform for controlled delivery of nanocarriers.