Supramolecular copolymers can not only enrich the diversity of the polymer backbone but also exhibit certain special and improved properties compared with supramolecular homopolymers. However, the synthesis procedure of supramolecular copolymers is relatively complicated and time‐consuming. Herein, a simple transformation from an AB2‐based supramolecular hyperbranched homopolymer to an AB2+CD2‐based supramolecular hyperbranched alternating copolymer by the “competitive self‐sorting” strategy is reported. After adding CD2 monomer, which bears a competitive neutral guest moiety ( TAPN ) and two receptive benzo‐21‐crown‐7 host moieties ( B21C7 ), to the as‐prepared AB2‐type supramolecular hyperbranched homopolymer constructed by the self‐assembly of dialkylammonium salt ( DAAS , A group)‐functionalized pillar[5]arene ( MeP5 , B groups) monomers, the initial homopolymer structure is disrupted and then reassemble into a new supramolecular hyperbranched alternating copolymer based on the competitive self‐sorting interaction between MeP5 ‐ TAPN and B21C7 ‐ DAAS . This study supplies a convenient approach to directly transform supramolecular homopolymers into supramolecular copolymers.
For anion exchange membranes (AEMs), achieving efficient hydroxide conductivity without excessive hydrophilicity presents a challenge. Hence, new strategies for constructing mechanically strengthened and hydroxide conductive (especially at controlled humidity) membranes are critical for developing better AEMs. Macromolecular modification involving ylide chemistry (Wittig reaction) for the fabrication of novel AEMs with an interpenetrating polymer network structure is reported. The macromolecular modification is cost effective, facile, and based on a one‐pot synthesis. AEM water uptake is reduced to 3.6 wt% and a high hydroxide conductivity (69.7 mS cm−1, 90 °C) is achieved simultaneously. More importantly, the membrane exhibits similar tensile strength (>35 MPa) and comparable flexibility in both dry and wet states. These AEMs could find further applications within anion exchange membrane fuel cells with low humidity or photoelectric assemblies.
Hierarchical semicrystalline block copolymer nanoparticles are produced in a segmented gas‐liquid microfluidic reactor with top‐down control of multiscale structural features, including nanoparticle morphologies, sizes, and internal crystallinities. Control of multiscale structure on disparate length scales by a single control variable (flow rate) enables tailoring of drug delivery nanoparticle function including release rates.
This communication describes the first application of cycloaddition between an in situ generated nitrile oxide with norbornene leading to a polymer crosslinking reaction for the preparation of poly(ethylene glycol) hydrogels under physiological conditions. Hydrogels with high water content and robust physical strength are readily formed within 2–5 min by a simple two‐solution mixing method which allows 3D encapsulation of neuronal cells. This bioorthogonal crosslinking reaction provides a simple yet highly effective method for preparation of hydrogels to be used in bioengineering.
A novel strategy for the incorporation of carbon dioxide into polymers is introduced. For this purpose, the Ugi five‐component condensation (Ugi‐5CC) of an alcohol, CO2, an amine, an aldehyde, and an isocyanide is used to obtain step‐growth monomers. Polymerization via thiol‐ene reaction or polycondensation with diphenyl carbonate gives diversely substituted polyurethanes or alternating polyurethane‐polycarbonates, respectively. Furthermore, the application of 1,12‐diaminododecane and 1,6‐diisocyanohexane as bifunctional components in the Ugi‐5CC directly results in the corresponding polyamide bearing methyl carbamate side chains ( = 19 850 g mol−1). The latter polymer is further converted into the corresponding polyhydantoin in a highly straightforward fashion.
Dispersions of short electrospun fibers are utilized for the preparation of nanofiber nonwovens with different weight area on filter substrates. The aerosol filtration efficiencies of suspension‐borne nanofiber nonwovens are compared to nanofiber nonwovens prepared directly by electrospinning with similar weight area. The filtration efficiencies are found to be similar for both types of nonwovens. With this, a large potential opens for processing, design, and application of new nanofiber nonwovens obtained by wet‐laying of short electrospun nanofiber suspensions.
Polyacrylamides containing pendant aminobisphosphonate groups are synthesized via reversible addition‐fragmentation chain transfer (RAFT) polymerization and a multicomponent postpolymerization functionalization reaction. A Moedritzer–Irani reaction installs the phosphonic acid groups on well‐defined, RAFT‐generated polymers bearing a pendant amine. An alternate route to the same materials is developed utilizing a three‐component Kabachnik–Fields reaction and subsequent dealkylation. Kinetics of the RAFT polymerization of the polymer precursor are studied. Successful functionalization is demonstrated by NMR and FTIR spectroscopy and elemental analysis of the final polymers.
A novel application of supramolecular interactions within semicrystalline polymers, capable of self‐assembling into supramolecular polymer networks via self‐complementary multiple hydrogen‐bonded complexes, is demonstrated for efficient construction of highly controlled self‐organizing hierarchical structures to offer a direct, efficient nucleation pathway resulting in superior crystallization performance. Herein, a novel functionalized poly(ε‐caprolactone) containing self‐complementary sextuple hydrogen‐bonded uracil‐diamidopyridine (U‐DPy) moieties is successfully developed and demonstrated excellent thermal and viscoelastic properties as well as high dynamic structural stability in the bulk state due to physical cross‐linking created by reversible sextuple hydrogen bonding between U‐DPy units. Due to the ability to vary the extent of the reversible network by tuning the U‐DPy content, this newly developed material can be readily adjusted to obtain the desired crystalline products with specific characteristics. Importantly, incorporating only 0.1% U‐DPy resulted in a polymer with a high crystallization rate constant, short crystallization half‐time, and much more rapid crystallization kinetics than pristine PCL, indicating a low content of U‐DPy moieties provides highly efficient nucleation sites that manipulate the nucleation and growth processes of polymer crystals to promote crystallization and chain alignment in bulk. This new system is suggested as a potential new route to substantially improve the performance of polymer crystallization.
Integrating irreplaceable features of both covalent chemistry and noncovalent interactions into a single entity to maximize the applicability is highly desired. Here, a discovery of this type of hybrid, developed by Stupp and co‐workers, is developed, where a synergistic combination of covalent and noncovalent compartments enables them to assemble by each other perfectively. The covalent compartments can grow into polymer chains assisted by a supramolecular compartment. The supramolecular compartments can be reversibly removed and re‐formed to reconstitute the hybrid structure. The obtained soft materials can serve as functional platforms for molecular delivery or self‐repairing materials.
Core cross‐linked star (CCS) polymers become increasingly important in polymer science and are evaluated in many value‐added applications. However, limitations exist to varied degrees for different synthetic methods. It is clear that improvement in synthetic efficiency is fundamental in driving this field moving even further. Here, the most recent advances are highlighted in synthetic strategies, including cross‐linking with cross‐linkers of low solubility, polymerization‐induced self‐assembly in aqueous‐based heterogeneous media, and cross‐linking via dynamic covalent bonds. The understanding of CCS polymers is also further refined to advocate their role as an intermediate between linear polymers and polymeric nanoparticles, and their use as interfacial stabilizers is rationalized within this context.
A heterotritopic copillar[5]arene monomer by introducing effective neutral guest moieties (methylene chains end‐capped with cyano and triazole groups) to a pillar[5]arene macrocycle is prepared. This well‐designed AB2‐type copillar[5]arene contains strong host–guest recognition motifs that are connected with relatively flexible and long linkers, thus efficiently assembles to form supramolecular hyperbranched polymer (SHP) in chloroform solution, which is characterized by various techniques including 1H NMR, DOSY, viscosity, DLS, and TEM. Particularly, this supramolecular polymer can be effectively depolymerized by adding a competitive butanedinitrile guest.
A novel one‐component type II polymeric photoinitiator, poly(vinyl alcohol)–thioxanthone (PVA–TX), is synthesized by a simple acetalization process and characterized. PVA–TX enables photopolymerization of methyl methacrylate and acrylamide in both organic and aqueous media. Photopolymerization proceeds even in the absence of a co‐initiator since PVA–TX possesses both chromophoric and hydrogen donating sites in the structure.
The development of a straightforward method is reported to form hybrid polymer/gold planet–satellite nanostructures (PlSNs) with functional polymer. Polyacrylate type polymer with benzyl chloride in its backbone as a macromolecular tracer is synthesized to study its localization within PlSNs by analyzing the elemental distribution of chlorine. The functionalized nanohybrid structures are analyzed by scanning transmission electron microscopy, electron energy loss spectroscopy, and spectrum imaging. The results show that the RAFT (reversible addition–fragmentation chain transfer) polymers' sulfur containing end groups are colocalized at the gold cores, both within nanohybrids of simple core–shell morphology and within higher order PlSNs, providing microscopic evidence for the affinity of the RAFT group toward gold surfaces.
The different mechanisms contributing to adhesion between two polymer surfaces are summarized and described in individual examples, which represent either seminal works in the field of adhesion science or novel approaches to achieve polymer–polymer adhesion. A further objective of this article is the development of new methodologies to achieve strong adhesion between low surface energy polymers.
Flexible, tough, and self‐healable polymeric materials are promising to be a solution to the energy problem by substituting for conventional heavy materials. A fusion of supramolecular chemistry and polymer chemistry is a powerful method to create such intelligent materials. Here, a supramolecular polymeric material using multipoint molecular recognition between cyclodextrin (CD) and hydrophobic guest molecules at polymer side chain is reported. A transparent, flexible, and tough hydrogel (host–guest gel) is formed by a simple preparation procedure. The host–guest gel shows self‐healing property in both wet state and dry state due to reversible nature of host–guest interaction. The practical utility of the host–guest gel as a scratch curable coating is demonstrated.
The nanostructures of thin films spin‐coated from binary blends of compositionally symmetric polystyrene‐b‐polybutadiene (PS‐b‐PB) diblock copolymer having different molar masses are investigated by means of atomic force microscopy (AFM) and grazing‐incidence small‐angle X‐ray scattering (GISAXS) after spin‐coating and after subsequent solvent vapor annealing (SVA). In thin films of the pure diblock copolymers having high or low molar mass, the lamellae are perpendicular or parallel to the substrate, respectively. The as‐prepared binary blend thin films feature mainly perpendicular lamellae in a one‐phase state, indicating that the higher molar mass diblock copolymer dominates the lamellar orientation. The lamellar thickness decreases linearly with increasing volume fraction of the low molar mass diblock copolymer. After SVA, well‐defined macrophase‐separated nanostructures appear, which feature parallel lamellae near the film surface and perpendicular ones in the bulk.
Micromolding surface‐initiated polymerization enables the fabrication of polymer coatings that reproduce the microscale surface topography of superhydrophobic leaves onto solid supports. Here, the surfaces of superhydrophobic leaves from Trifolium repens and Aristolochia esperanzae are molded and reproduced as the topography of a partially fluorinated polymer coating through the surface‐initiated ring‐opening metathesis polymerization of 5‐(perfluorooctyl)norbornene (NBF8). The polymer coatings have thicknesses exceeding 100 μm, which can be tailored by the amount of monomer added to the mold. These coatings are robustly bound to the substrate, contain compositions not found in nature, and achieve superhydrophobicity that is comparable to the actual leaf.
Poly‐(N‐isopropylacrylamide) (PNIPA) hydrogel films doped with uniaxially aligned liquid crystalline (LC) nanosheets adsorbed with a dye are synthesized and its anomalous photothermal deformation is demonstrated. The alignment of the nanosheet LC at the cm‐scale is easily achieved by the application of an in‐plane or out‐of‐plane AC electric field during photo‐polymerization. A photoresponsive pattern is printable onto the gel with μm‐scale resolution by adsorption of the dye through a pattern‐holed silicone rubber. When the gel is irradiated with light, only the colored part is photothermally deformed. Interestingly, the photo‐irradiated gel shows temporal expansion along one direction followed by anisotropic shrinkage, which is an anomalous behavior for a conventional PNIPA gel.
This communication reports the first example of precision polyolefin nanoalloys where an exotic immiscible polymer is nanometrically dispersed with stability in a polyolefin matrix in a highly controlled mode. Following the preparation of polypropylene/multiwalled carbon nanotubes nanocomposites (PP/MWCNTs) by in situ Ziegler‐Natta polymerization, the hydroxyl groups on the surfaces of individual MWCNTs are used to initiate ring‐opening polymerization of ε‐caprolactone, resulting in PP/poly(ε‐caprolactone) (PCL) alloy with PCL grafted on MWCNTs. Upon phase formation, the PP/MWCNTs‐g‐PCL alloys exhibit a unique PCL dispersion morphology, which is stable and solely governed by PCL molecular weight.
Supramolecular polymer networks and gels often exhibit three effects in rheology as a function of increasing strength and extent of transient chain interlinkage: (i) the longest relaxation time increases, (ii) the elastic part of the complex shear modulus on timescales longer than that increases, and (iii) the frequency‐dependent power‐law scaling of this modulus gets shallower in this regime. In a recent report, these effects have been systematically assessed by comparing transient polymer networks derived from a common precursor modified with different extents of a common hydrogen‐bonding supramolecular sticker. In this communication, complementary studies are discussed that are based on a set of polymers also derived from a common precursor but all modified with the same extent (4.8%) of very different supramolecular crosslinking motifs. This comparison reveals that effect (iii) can be rationalized by exacerbation of polydispersity effects to the relaxation time spectrum if supramolecular interchain sticking is present. In addition, effect (ii) is addressable to a simple thermodynamic argument that appraises the supramolecular sticking contribution to the elastic part of the shear modulus in the relaxation regime.
