A recurring challenge in the field of nanocomposites is to control spatial distribution nanoparticles (NPs) a polymer matrix. This issue critical importance since it now well-established that specific NP dispersion state necessary optimize desired property (PNCs). Perspective focuses on one particular approach controlling dispersion, and hence properties polymer-based nanocomposites: use polymer-grafted NPs. Novel developments over past decade synthesis techniques allow us controllably...

The field of polymer nanocomposites has been at the forefront research in community for past few decades. Foundational work published Macromolecules during this time emphasized physics and chemistry inclusion nanofillers; remarkable early developments suggested that these materials would create a revolution plastics industry. After 25 years innovative groundbreaking research, PNCs have enabled many niche solutions. To complement extensive literature currently available, we focus Perspective...

A sol−gel process is described to produce phosphoric acid (PA)-doped polybenzimidazole (PBI) films that operate as fuel cell membranes above 150 °C for extended periods of time without the need feed gas humidification. When solutions high molecular weight heterocylic polymers such polybenzimidazoles in polyphosphoric (PPA) were cast into films, a transition from solution state gel was observed during hydrolysis solvent PPA (a good PBI) PA poor PBI). The resulting retained levels structure...

Reversible addition−fragmentation chain transfer polymerization (RAFT) was used to prepare polymer brushes grafted onto silica nanoparticles. Novel RAFT-silane agents were prepared that contained both an active RAFT moiety and a silane coupling agent. anchored nanoparticles by the functionalization of colloidal with agents. polymerizations then conducted from particle surface graft homopolymer block copolymer particles. The kinetics styrene (St) n-butyl acrylate (nBuA) investigated compared...

Abstract Long‐term durability testing of polybenzimidazole (PBI)‐based polymer electrolyte membrane (PEM) fuel cells was performed using test protocols designed to simulate cell operational situations which may be found in real applications. The voltages and phosphoric acid (PA) loss were carefully monitored over thousands hours hundreds cycles. In the typical operating range for high temperature PEM (160 °C), voltage degradation rate 4.9 μV h –1 steady‐state operation. PA rates generally...

Transparent polymer nanocomposites with high refractive index were prepared by grafting chains onto anatase TiO2 nanoparticlesvia a combination of phosphate ligand engineering and alkyne-azide "click" chemistry. Highly crystalline nanoparticles 5 nm diameter synthesized solvothermal method used as filler. The phosphate-azide anchors strongly the nanoparticle surface azide end group allows for attachment poly(glycidyl methacrylate) (PGMA) through an reaction. composite material increased...

We examine the structure of densely grafted polymer layers grown from surfaces spherical nanoparticles over a broad range graft densities and chain lengths. Dynamic light scattering (DLS) experiments show that hydrodynamic thickness layer, h, scales as h ∝ N4/5 for short chains high grafting densities, is, in concentrated brush (CPB) regime, whereas N3/5 long enough (semidilute brush, SDPB). The mean field theory Wijmans Zhulina is able to collapse approximately all our data those existing...

The field of polymer membrane design is primarily based on empirical observation, which limits discovery new materials optimized for separating a given gas pair. Instead relying exhaustive experimental investigations, we trained machine learning (ML) algorithm, using topological, path-based hash the repeating unit. We used limited set permeability data six different gases in ~700 polymeric constructs that have been measured to date predict gas-separation behavior over 11,000 homopolymers not...

Abstract A series of polybenzimidazoles (PBIs) incorporating main chain pyridine groups were synthesized from the dicarboxylic acids (2,4‐, 2,5‐, 2,6‐ and 3,5‐) 3,3′,4,4′‐tetraaminobiphenyl, using polyphosphoric acid (PPA) as both solvent polycondensation reagent. novel process, termed PPA has been developed to prepare phosphoric (PA) doped PBI membranes by direct‐casting polymerization solution without isolation or re‐dissolution polymers. The subsequent hydrolysis PA moisture absorbed...

Well-defined polymer brushes grafted onto silica nanoparticles were prepared by reversible addition−fragmentation chain transfer polymerization (RAFT). A versatile RAFT agent, 4-cyanopentanoic acid dithiobenzoate (CPDB), was attached to amino-functionalized colloidal direct condensation of the mercaptothiazoline-activated CPDB with surface amino groups. polymerizations then conducted from particle graft particles. The kinetics methyl methacrylate and styrene investigated compared model...

We critically explore the role of particle dispersion on melt state mechanical properties nanocomposites formed by mixing polystyrene homopolymers with grafted silica nanoparticles. selected this system since we previously showed that nanoparticle spatial distribution can be controlled through judicious choices brush and matrix parameters. Here focus temporal evolution self-assembly its effect reinforcement using rheology, electron microscopy, measurement nanoscale dynamics X-ray photon...

High molecular weight, highly PA-doped s-PBI membranes have been developed with robust mechanical properties and excellent proton conductivities (>0.1 S cm−1) at elevated temperatures (>100 °C). These show high PA loadings of 30−35 mol PA/PBI, average tensile stress strain 0.804 MPa 69.64%, respectively. Proton were dependent on the acid doping level measured between 0.1 0.25 cm−1 180 °C, a pronounced increase over most phosphoric acid-doped sulfonated PBI to date. Preliminary fuel cell...

Abstract We show that the thermomechanical properties of polymer nanocomposites are critically affected by polymer‐particle wetting behavior. Silica nanoparticles grafted with dense polystyrene brushes degree polymerization 1050 blended melts to form nanocomposites. It was found low molecular weight (MW) lengths <880 wet these particles. Concurrently, glass transition temperature ( T g ) nanocomposite increases. At higher MW, matrix does not particles and decreases. © 2006 Wiley...

We critically leverage the fact that polymer grafted nanoparticles behave akin to block copolymers systematically vary nanoparticle dispersion and examine its role on mechanical reinforcement in liquid-polymer-based nanocomposites. The are noncontacting, we perform rheological measurements 80K above polymer's glass transition temperature. Our rheology results unequivocally show is maximized by formation of a transient, but long-lived, percolating polymer–particle network with particles...

RAFT (reversible addition–fragmentation chain transfer) polymerization has been widely used to synthesize different polymer architectures such as brushes on nanoparticles for incorporation into nanocomposites. It is believed that these brushes, with the same chemistry matrix polymer, can be employed improve filler dispersion by compatibilizing unfavorable enthalpic interactions between inorganic and their organic host matrices. However, monomodal brush graft are found aggregate a range of...

Polybenzimidazole (PBI) derivatives having dihydroxy functional groups (poly(2,2′-(dihydroxy-1,4-phenylene)5,5′-bibenzimidazole), 2OH-PBI) were successfully synthesized in poly(phosphoric acid) (PPA). The 2OH-PBI polymer underwent cross-linking reactions during the polymerization via formation of phosphate bridges between hydroxy backbone. Gelation solution was avoided by conducting at relatively low monomer concentrations. membranes showed higher proton conductivity compared to...

It is commonly accepted that the addition of spherical nanoparticles (NPs) cannot simultaneously improve elastic modulus, yield stress, and ductility an amorphous glassy polymer matrix. In contrast to this conventional wisdom, we show can be substantially increased, while maintaining gains in modulus nanocomposite films composed silica NPs grafted with polystyrene (PS) chains a PS The key these improvements are (i) uniform NP spatial dispersion (ii) strong interfacial binding between matrix,...

A functional monomer with a pendant azide moiety, 6-azidohexyl methacrylate (AHMA), was polymerized on the surface of silica nanoparticles via surface-initiated reversible addition−fragmentation chain transfer (RAFT) polymerization considerable control over molecular weight and distribution. The kinetics AHMA mediated by 4-cyanopentanoic acid dithiobenzoate (CPDB) anchored investigated compared that free CPDB under similar conditions. subsequent postfunctionalizations PAHMA-grafted were...

Tuning the dispersion of inorganic nanoparticles within organic matrices is critical to optimizing polymer nanocomposite properties and intrinsically difficult due their strong enthalpic incompatibility. Conventional attempts use brushes control nanoparticle are challenged by need for high graft density reduce particle core–core attractions low entropic penalty matrix penetration into brush. We validated a parametric phase diagram previously reported Pryamtisyn et al. (Pryamtisyn, V.;...

One key to optimizing the performance of polymer nanocomposites for high-tech applications is surface ligand engineering nanofiller, which has been used either tune nanofiller morphology or introduce additional functionalities. Ligand can be relatively simple such as a single population short molecules on nanoparticle designed matrix compatibility. It also have complexity that includes bimodal (or multimodal) populations ligands enable independent control enthalpic and entropic interactions...