Aggregation Behavior Of Polymers Research Articles

Recent Progress of All Polymer Solar Cells with Efficiency Over 15%

All polymer solar cells (APSCs) composed of polymeric donors and acceptors have attracted tremendous attention due to their unique merits of mechanical flexibility and good film formation property, which exhibit promising applications on wearable and flexible stretchable devices. Over 18% power conversion efficiency of APSCs has been achieved benefiting from the continuous development of functional layer materials innovation and device engineering evolution. In this review, the functional layer materials that enabled the recent progress of efficient APSCs are outlined, including typical polymer donors, emerging polymer acceptors based on polymerizing small molecule acceptors strategy, interfacial materials as well as the rational design rules for corresponding functional materials. From the perspective of device engineering evolution, the film deposition and treatment techniques are introduced, which play a vital role in manipulating film morphology through properly tuning the vertical component distribution and aggregation behavior of polymers. Meanwhile, the ternary strategy is also discussed as an effective method in promoting mechanical durability, stability, and thickness‐insensitive characteristics of APSCs facing for future applications. The challenges and outlooks on this filed are finally proposed for developing high‐performance APSCs.

Phase Control Behavior of Lateral Polymer Photodetectors Using Strong Aggregation Bulk Heterojunction Film

AbstractThe aggregation behavior of polymers can ultimately have a significant impact on the performance of polymer photodetectors depends mainly on the main solvent, solvent additive, thermal annealing treatment, and so on. In this work, a phase control behavior of lateral polymer photodetectors (L‐PPDs) is realized by changing the acceptor concentration or introducing 1,8‐diiodooctane (DIO) in strong aggregation of bulk heterojunction (BHJ) films, which can effectively regulate the minority carriers trapping under high PC61BM ratio. Additionally the responsivity (R), gain (G) and specific detectivity (D*) value of the L‐PPDs can reach 94.4 A W−1, 289.7, and 1.33 × 1014 Jones under 0.0031 mW cm−2 @405 nm, respectively. The structure of the L‐PPDs is optimized as quartz/ PMMA (30 nm)/ PffBT4T‐2OD:PC61BM (D/A ratio = 1:1.2)/ Ag–Ag electrodes. Furthermore, the phase separation of the thin films is promoted by introducing 3% DIO, resulting in a clear increase of response speed (fall time is about tenfold faster than that of the control device), and an improved switching performance about 60‐fold higher under strong light (10.42 mW cm−2). This research represents an important step forward in the fabrication of high‐performance polymer photodetectors, which show promising application potential.

Confinement of a polymer chain: An entropic study by Monte Carlo method

The properties of macromolecules in presence of an interface could be considerably modified due to confinement effects. When phase separations are performed in nanoconfined domains, the concurrent presence of high‐energy interfaces and conformational entropy constraints of the macromolecules causes profound differences in polymer aggregation behavior. Here, thermodynamics of a polymer chain in solution, confined by a three‐dimensional cubic interface, is studied by means of Monte Carlo method, focusing on the chain conformational entropy penalty arising from the excluded volume effects. The presented method might become a general tool for a preliminary evaluation of the thermodynamic effects due to the confinement of a polymer system. Further, the interface effects on Thermally Induced Phase Separation (TIPS) of polymer solutions, confined by High‐Pressure Homogenization, are experimentally studied, regarding final morphologies. It is confirmed how peculiar polymer morphologies are obtained only when the TIPS develops under nanoconfinement degrees above a threshold one. © 2017 American Institute of Chemical Engineers AIChE J, 64: 416–426, 2018

Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives.

A facile method for the preparation of polycarbodiimide-based secondary structures (e.g., nano-rings, "craters," fibers, looped fibers, fibrous networks, ribbons, worm-like aggregates, toroidal structures, and spherical particles) is described. These aggregates are morphologically influenced by extensive hydrophobic side chain-side chain interactions of the singular polycarbodiimide strands, as inferred by atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques. Polycarbodiimide-g-polystyrene copolymers (PS-PCDs) were prepared by a combination of synthetic methods, including coordination-insertion polymerization, copper(I)-catalyzed azide alkyne cycloaddition (CuAAC) "click" chemistry, and atom transfer radical polymerization (ATRP). PS-PCDs were found to form specific toroidal architectures at low concentrations in CHCl3. To determine the influence of a more polar solvent medium (i.e., THF and THF/EtOH) on polymer aggregation behavior, a number of representative PS-PCD composites have been tested to show discrete concentration-dependent spherical particles. These fundamental studies are of practical interest to the development of experimental procedures for desirable architectures by directed self-assembly in thin film. These architectures may be exploited as drug carriers, whereas other morphological findings represent certain interest in the area of novel functional materials.

Effects of the Type of Solvents on the Morphology of Styrene-Methacrylic Acid Random Copolymers Cast onto Silicon Wafer

The effects of the type of solvents on the aggregation behavior of poly(styrene-ran-methacrylic acid) (PSMAA) cast onto silicon wafer were studied using a SEM method. It was found that polystyrene prepared from DMF formed non-spherical aggregates but that PSMAA formed mixtures of ellipsoids and spheres. As the acid content increased, the spheres having a distinct boundary started contacting each other, and the average size of spherical particles decreased. Upon neutralization, the spherical particles became contacted spheres covered with much smaller spheres (ca. 20 nm in their sizes) and formed micro-gels. These results were compared to the data in the previous study of samples obtained from either water or THF. It was observed that the solubility parameters of the copolymers and ionomers, and polarity of solvents were some of key factors that determine the aggregation behavior of the polymers. The volatility of the solvent was also found to be an important factor for the aggregation behavior of polymers.

Aggregation Behavior of Amphiphilic Statistical Polymers and Their Interactions with Nonionic Surfactants

A series of amphiphilic polymers were synthesized by the statistical polymerization of 2-(acrylamido)-dodecanesulfonic acid (AMC12S) with 2-(acrylamido)-2-methylpropanesulfonic acid (AMPS) and they contained a high mole fraction of AMC12S (X=0.1,0.3,0.5). The aggregation behaviors of the polymers and their interactions with three nonionic surfactants HO(CH2CH2O)10C12H25 (C12E10),HO(CH2CH2O)20C12H25 (C12E20),and HO(CH2CH2O)40C12H25 (C12E40) in aqueous solutions were investigated by steady-state fluorescence and quasi-elastic light scattering measurements. The effect of X on the association performance and the influence of the surfactant's hydrophilic group length on these interactions were also investigated. The critical aggregation concentration (CAC) of the polymer was found to significantly decrease with increasing X. The CAC of the polymer with X=0.5 is as low as 0.0039 g·L-1. The hydrodynamic sizes of the aggregates (Rh) are larger than 26 nm and increase with an increase in polymer concentration,indicating that the polymeric molecules exhibit a strong tendency for interpolymer association,leading to the formation of multimolecular aggregates. When X increases,both Rh and its tendency to increase decrease,suggesting that the aggregates becomemore compact. The interaction between surfactant and polymer is very strong and the polymer aggregates begin to collapse when the surfactant concentration reaches the critical micelle concentration (CMC) in the mixed solutions and mixed aggregates form. The destructive ability of the surfactant increases as the length of the hydrophilic group increases. The Rh value of the mixed aggregates formed by C12E40 and the polymer with X=0.5 is 6.8 nm,which is consistent with the Rh value of the C12E40 aggregates.