Glassy organic semiconductors provide a convenient host for dispersing guest molecules, such as dopants or light-emitting chromophores. However, many glass-forming compounds will crystallize over time leading to changes in performance and stability in devices. Methods to stabilize amorphous molecular solids are therefore desirable. We demonstrate that solution-processable glasses can be formed from a mixture of 8,8′-biindeno[2,1-b]thiophenylene (BTP) atropisomers. While the trans isomer of methylated BTP, (E)-MeBTP crystallizes in spin-cast films, the addition of (Z)-MeBTP slows the growth of the spherulites. X-ray scattering and optical microscopy indicate that films containing 40% (Z)-MeBTP do not crystallize, even with the addition of nucleation agents and aging for several months.

Applications of polymer thin films include functional coatings, flexible electronics, membranes and energy conversion. The physical properties of polymer films of nanoscale thicknesses typically differ from the bulk, due largely to entropic effects and to enthalpic interactions between the macromolecules and the external interfaces. Studies of the size-dependent physical properties of macromolecules have largely been devoted to linear chain polymers. In this Prospective, we review recent experiments and simulations that describe the structure and fascinating physical properties, from wetting to the glass transition, of star-shaped macromolecules. The properties of these molecules would render them more useful than their linear chain analogs, for some specific applications.

The chemical diversity of organic semiconductors coupled with the kinetic nature of film formation make it challenging to tune the structure of active-layer thin films in organic electronics across multiple length scales. We review techniques to tune aspects of film structure within a framework that accounts for the competition between the time available for structural development and the time required by the organic semiconductors to order, defined by a dimensionless time, τ, that describes the ratio of these two quantities. By considering these two competing time scales, we propose general guidelines to tune the film structure accordingly.

Polymer-based nanomaterials have captured increasing interest over the past decades for their promising use in a wide variety of applications including photovoltaics, catalysis, optics, and energy storage. Bottom-up assembly engineering based on the self- and directed-assembly of polymer-based building blocks has been considered a powerful means to robustly fabricate and efficiently manipulate target nanostructures. Here, we give a brief review of the recent advances in assembly and reconfigurability of polymer-based nanostructures. We also highlight the role of computer simulation in discovering the fundamental principles of assembly science and providing critical design tools for assembly engineering of complex nanostructured materials.

Poly[sulfur-random-1,3-diisopropenylbenzene (DIB)] copolymers synthesized via inverse vulcanization form electrochemically active polymers used as cathodes for high-energy density Li–S batteries, capable of enhanced capacity retention (1005 mAh/g at 100 cycles) and lifetimes of over 500 cycles. In this prospective, we demonstrate how analytical electron microscopy can be employed as a powerful tool to explore the origins of the enhanced capacity retention. We analyze morphological and compositional features when the copolymers, with DIB contents up to 50% by mass, are blended with carbon nanoparticles. Replacing the elemental sulfur with the copolymers improves the compatibility and interfacial contact between active sulfur compounds and conductive carbons. There also appears to be improvements of the cathode mechanical stability that leads to less cracking but preserving porosity. This compatibilization scheme through stabilized organosulfur copolymers represents an alternative strategy to the nanoscale encapsulation schemes which are often used to improve the cycle life in high-energy density Li–S batteries.

Polymers with stable radical groups are promising materials for organic electronic devices due to their unique redox activity. Block copolymers with one redox active block could be used in nanostructured devices for electronic applications. We report on the synthesis and characterization of such multifunctional block copolymers in which phase separation on the 10 nm (half pitch) scale is achieved by using fluorinated blocks. Fluorination of one block increases the degree of phase separation and leads to smaller accessible domain sizes. Block copolymers with 60%, 80% and 90% of a stable radical containing block and either fluorinated or non-fluorinated second blocks were made by atom transfer radical polymerization, and their microstructure formation as a function of fluorine content is described after solvent vapor or thermal annealing. Electrical characterization of such a partly fluorinated block copolymer shows their potential for electronic devices.

Solubilizing alkyl chains play a crucial role in the design of semiconducting polymers because they define the materials solubility and processability as well as both the crystallinity and solid-state microstructure. In this paper, we present a scarcely explored design approach by attaching the alkyl side chains on one side (cis-) or on both sides (trans-) of the conjugated backbone. We further investigate the effects of this structural modification on the solid-state properties of the polymers and on the charge-carrier mobilities in organic thin-film transistors.

Electronic performance in semiconducting polymers has improved dramatically in recent years owing to a host of novel materials and processing techniques. Our understanding of the factors governing charge transport in these materials has also been enhanced through advancements in both experimental and computational techniques, with disorder appearing to play a central role. In this prospective, we propose that disorder is an inextricable aspect of polymer morphology which need not be highly detrimental to charge transport if it is embraced and planned for. We discuss emerging guidelines for the synthesis of polymers which are resilient to disorder and present our vision for how future advances in processing and molecular design will provide a path toward further increases in charge-carrier mobility.

The introduction of functional units onto semiconducting polymers either as side chains or at the α- and ω-ends of polymeric chains is the method of choice in order to impose additional functions to the final semiconducting materials when aiming specific applications. Moreover, the functionalization approach provides a route to further complex macromolecular architectures as well as the generation of hybrid materials through the covalent attachment of the semiconductor to carbon nanostructures or to inorganic nanoparticles. Via this prospective an outline over functionalized and hybrid semiconducting polymers is provided along with possible paths of future research toward functional and hybrid semiconductors.

Material research and development is increasingly focusing on achieving specialized functionality in materials. For example, the ability to “self-heal (SH)”, or naturally repair accrued damage, is attractive because it extends the lifetime of the material by increasing resistance to damaging conditions and prolonging preservation of material properties. Additionally, shape memory (SM) materials, including SM polymers, are actively considered for their ability to change shape one or more times upon application of an external stimulus. Here, we present a polymer composite, composed of poly(vinyl acetate) (PVAc) and poly(ε-caprolactone) (PCL), exhibiting both SH and SM functionalities. In fact, the SM assists in the SH ability in a process developed by our group termed, shape memory-assisted self-healing (SMASH). The advantage of the SH composite presented here is its simple fabrication. Dual-electrospinning is used to simultaneously electrospin PVAc and PCL, achieving an interwoven polymeric composite of otherwise immiscible polymers. The dual-electrospinning method facilitates precise control of the relative weight fractions of the components, and thus allows for tuning of the material properties. Upon thermal activation, damaged PVAc–PCL composites exhibited SH under a variety of testing conditions. Furthermore, the composites exhibited impressive dual and triple SM capabilities in the dry and hydrated states, respectively. Together, the commercial availability of the components and the simplicity of preparation translate to a SMASH system that could be mass produced and used as a SH coating or alone, as a packaging material.

We report on the ability to switch an optical material composed of a polymer stabilized cholesteric liquid crystal (polymer stabilized cholesteric texture, PSCT) between stable transparent (reflective) and scattering modes. The degree of scattering is controllable with the strength of the applied electric field. The mechanism for bistable switching of the PSCT is distinguished from prior examinations by employing electromechanical displacement of a stabilizing polymer network. The stable transparent (reflective) or scattering modes are induced with a variety of driving schemes employing both alternating and direct current fields. The relative degree of scattering can be varied to allow for grayscale control potentially useful in smart window and display applications.

We report the use of electrospray to continuously deposit thin films, including patterned films, of a block copolymer (BCP). High substrate temperatures led to vertically oriented cylindrical microdomains at the film surface independent of the solvent composition and deposition rates utilized. Conversely, low substrate temperatures resulted in morphologies that were more sensitive to these parameters, with poorly ordered films of globular structures observed at the lowest temperatures considered. The deposition pattern is defined by spatially varying the electric field at the substrate using an underlying charged grid. These results open up new possibilities for patterned deposition of BCP films with morphological control.

All-polymer solar cells composed of binary blends of donor poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiophene-)-2–6-diyl)] (PBDTTT-CT ), and acceptor polymers naphthalene diimide-selenophene copolymer (PNDIS-HD) and perylene diimide-selenophene copolymer (PPDIS) had power conversion efficiencies (PCEs) of 1.3 and 2.1%, respectively. Ternary blend solar cells composed of [PBDTTT-CT][PNDIS-HD]1−x[PPDIS]x at 75 wt% PPDIS had a PCE of 3.2%, which is about a 50%–140% enhancement compared with the binary blend devices. Equality of the ternary blend short-circuit current to the sum of those of the binary blend devices, among other results, provided evidence of a parallel-like bulk heterojunction mechanism in the ternary blend solar cells. These results provide the first example of enhanced performance in ternary blend all-polymer solar cells.

The thermal history of amorphous polymers near the glass-transition temperature determines the extent to which macromolecules structurally relax, and ultimately their properties. Here, we report the correlation between physical aging, dielectric breakdown, and capacitive energy storage of polystyrene, poly(methyl-methacrylate), and associated silica nanocomposites. Guided by enthalphic recovery rates, dielectric breakdown strength increased from 20% to 40% when aged at Tg−10 °C before use. The generality of improvement and connection to enthalpic recovery afford a means to design pre-service processing of new polymers and additive manufacturing techniques to reduce excess volume within the glass; and thereby reduce initiation and inhibit propagation of electronic failure.

Depolymerizable polymers are stimuli-responsive materials triggered to depolymerize rapidly and completely into their constituent monomers on command. Applications include triggerable vehicles for controlled release, restructurable materials, disappearing or sacrificial composites, and lithographic resists. Owing to their widespread utility, significant efforts have aimed to prepare and explore depolymerizable polymers and their corresponding triggers. This “Prospective” highlights advances since their discovery over a half-century ago, discusses methods in their preparation, and presents recent developments in triggered depolymerization. It also surveys applications that harness these polymers’ unique properties, while offering insights into research directions that may contribute to progress in this dynamic field.

The design of π-conjugated molecules and polymers has driven the increase in efficiency of bulk heterojunction organic photovoltaic devices from <1% to over 12%. The pathways to generation of free charge carriers are still being uncovered. By focusing on blends of conjugated polymers with fullerenes, recent work has highlighted the impact of the design of donor–acceptor polymers on optoelectronic properties and phase-separated morphologies. This morphology of the active layer is largely controlled by processing conditions, such as use of processing additives. Developing a deep understanding of the impact of polymer chemistry and processing at the laboratory scale is key to translating the technology of organic photovoltaics from the research scale to large-area modules.

Electronically active block polymers based on π-conjugated macromolecules have been investigated for applications where nanostructured electrodes are of prime import; however, controlling the nanoscale order of these materials has proven challenging. Here, we demonstrate that diblock copolymers that utilize a non-conjugated radical polymer moiety as the electronically active block assemble into ordered thin-film nanostructures. Specifically, the diblock copolymer polydimethylsiloxane-b-poly(2,2,6,6-tetramethylpiperidinyloxy methacrylate) (PDMS–PTMA) was synthesized via atom transfer radical polymerization to generate polymers with readily controlled molecular properties. Importantly, solvent annealing of the PDMS–PTMA thin films led to well-defined nanostructures with domain spacings of the order of ~30–40 nm.

A model with which to predict the effect of coplanar electrode geometry on diffraction uniformity in photorefractive polymer display devices was developed. Assumptions made in the standard use cases are no longer valid in the regions of extreme electric fields present in this type of device. Using electric-field induced second-harmonic generation through multiphoton microscopy, the physical response in regions of internal electric fields which fall outside the standard regimes of validity were probed. Adjustments to the standard model were made and the results of the new model corroborated through holographic four-wave mixing measurements.

Conjugated polymers (CPs) are widely investigated because of their intriguing optical and semiconducting properties in various optoelectronic device applications. Because of the one-dimensional p-orbital overlap along the main chain, CPs exhibit strong anisotropy in optoelectronic characteristics. Therefore, macroscopic assembly and alignment of CPs are essential to fully utilize their potential properties in real device applications. Here we review various processing strategies and material design principles for efficient CP alignment that result in highly anisotropic optical and electronic characteristics. Furthermore, we thoroughly review the incorporation of aligned CPs layers in organic light-emitting diodes, organic thin film transistors, and organic photovoltaic devices. The achieved macroscopic CP alignment has increased the optoelectronic properties and greatly improved device performance.