We report the detailed characterization of micelles formed by two nonionic, amphiphilic ABC triblock copolymers. Poly(ethylene oxide)-b-poly(styrene)-b-1,2-poly(butadiene) (PEO-b-PS-b-PB) triblock copolymer "OSB" forms core-corona spherical micelles in aqueous solution, and the two hydrophobic blocks S and B are mixed homogeneously within the micelle core. PEO-b-PS-b-PB:C6F13I triblock copolymer "OSF" was prepared by selective fluorination of the B block in OSB with n-perfluorohexyl iodide. Fluorination of the B block induces internal segregation into an inner F core and an intermediate S shell. Furthermore, the strong incompatibility that results from fluorination drives a shape change into an oblate ellipsoid. These micellar morphologies are confirmed by combined light, neutron, and X-ray scattering measurements, as well as TEM imaging.

The effect of difluorocarbene (CF2) modification on the self-assembly of polystyrene-bpolyisoprene (PS-b-PI) copolymers was investigated. We prepared a set of fully CF2-modified PS-b-PI copolymers (PS-b-FPI) with different molecular weights (8-13 kg/mol) and located their order-disorder transition temperatures (TODT) by rheology and static birefringence. Using both mean-field and fluctuation theory, we determined the temperature dependence of the interaction parameter between the styrene and CF2-modified isoprene segments (χSFI). Two series of polystyrene-b-(partially CF2-modified polyisoprene) (PS-b-(FPI-s-PI)) materials with different levels of CF2 modification were also prepared from the reaction between difluorocarbene and two nearly symmetric PS-b-PI precursors with molecular weights of 18 and 61 kg/mol, respectively. A lamellar morphology was established for all of the PS-b-(FPI-s-PI) copolymers below the TODT by small-angle X-ray scattering (SAXS) and rheology. The effective interaction parameter (χeff) between the PS and FPI-s-PI blocks, calculated from the domain spacing determined by SAXS, passes through a minimum before increasing smoothly by a factor of 4 upon complete CF2 modification. Using the binary interaction model originally developed for homopolymer/copolymer blends, we were able to understand the dependence of the χeff on the CF2-modification extent in a quantitative manner and extracted the three pairwise interaction parameters. Rheology and static birefringence were also used to locate the TODT for the lower molecular weight PS-b-(FPI-s-PI) series. The TODT was found to behave in a manner similar to the χeff: a decrease was observed at initial CF2 modification, and a sharp increase was observed upon further CF2 modification.

We have developed a simple and mild method for the fluorination of polybutadiene based on the addition of perfluoroalkyl iodides (RfI) to carbon−carbon double bonds. Triethylborane (Et3B) was utilized to initiate this free radical addition to model polybutadiene (PBD) homopolymers and a polystyrene−polybutadiene block copolymer at room temperature. Optimized reaction conditions led to consumption of more than 95% of the double bonds and preservation of narrow molecular weight distribution after the modification. We propose that the reaction undergoes a cyclization pathway rather than open-chain addition and that five-member ring structures are formed during the addition of RfI to 1,2-PBD. From 1H NMR spectroscopy, we estimate that 83% of the double bonds in the 1,2-PBD cyclized with their neighbors. This agrees well with a theoretical prediction by Flory for random irreversible cyclization between neighboring polymer repeat units. We also demonstrate the selective fluorination of the 1,2-PBD block in a polystyrene-block-1,2-polybutadiene (PS-b-1,2-PBD) copolymer. In contrast to the fluorinated homopolymers, subsequent hydrogenolysis of this fluorinated PS-b-1,2-PBD copolymer gave a soluble material. The 1H NMR spectrum and elemental analysis confirmed the complete hydrogenolysis. Preliminary physical characterization was performed by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), contact angle measurements, and small-angle X-ray scattering (SAXS). The glass transition temperature (T g) of the fluorinated 1,2-PBD increases by 75 °C, removal of the iodine in the fluorinated PS-b-1,2-PBD copolymer increases the thermal stability by ca. 100 °C, and all fluorinated polymers exhibit very low critical surface tensions (14−16 mN/m).

A series of partially fluorinated (C6F13H-modified) polystyrene-b-1,2-polybutadiene (PS-b-1,2-PB) copolymers were prepared by the reaction of a model PS-b-1,2-PB copolymer with n-C6F13I followed by substitution of hydrogen for the iodine by hydrogenolysis. The morphologies and domain spacings of the ordered samples at 120 and 195 °C were determined as a function of C6F13H modification extent using small-angle X-ray scattering (SAXS). From the domain spacings an effective interaction parameter (χeff) between the PS and partially C6F13H-modified 1,2-PB blocks was estimated. The χeff at 120 °C increases significantly with fluorination, from ca. 0.05 (0 mol % C6F13H modification) to ca. 0.75 (80 mol % C6F13H modification). The order−disorder transition temperature (T ODT) for a partially C6F13H-modified PS-b-1,2-PB (25 mol %) was determined to be 186 ± 3 °C, using rheology and static birefringence. From self-consistent mean-field theory χeff for this block copolymer is estimated to be 0.16 at T ODT, which agrees well with the value of 0.21 estimated from the domain spacing. These estimated interaction parameters demonstrate that a selective perfluoroalkylation approach can strongly enhance the incompatibility of PS-b-1,2-PB copolymers and is a powerful method for examining large regions of the block copolymer phase diagram with a single precursor molecule.

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The cloud-point behavior of fluorinated polyisoprenes (FPI) and fluorinated polybutadienes (FPBD) in supercritical fluid (SCF) CO2 are reported at temperatures from 60 to 170 °C and pressures from 1000 to 3000 bar. These fluorinated polymers were prepared by the addition of difluorocarbene (CF2) to the parent polydienes yielding a gem-difluorocyclopropane repeating unit, a segment containing both fluorine and a significant dipole moment. Neither the unmodified polyisoprene starting material nor the hydrogenated variant dissolves in CO2 up to temperatures of 155 °C and pressures of 2600 bar. Both FPI and FPBD dissolve in CO2, but pressures in excess of 1000 bar are needed to obtain a single phase. The PFI and PFBD cloud-point curves exhibit temperature minima at approximately 60 and 80 °C, respectively, likely due to an increase in CO2-CO2 and polymer-polymer interactions relative to polymer-CO2 interactions. As the amount of CF2 incorporation in FPI samples decreases, the cloudpoint curves shift to higher pressures and to higher temperatures. In a series of FPBD samples, an increase in cloud-point pressure with increase in molecular weight is initially large for molecular weights less than 10 5 and then becomes much less at higher molecular weights, as also observed for other polymer-SCF solvent mixtures. This methodology for incorporation of fluorine into macromolecules leads to significant enhancement of solubility in CO2.

Surface defects of perovskite films are the major sources of nonradiative recombination which limit the efficiency and stability of perovskite solar cells. Surface passivation represents one of the most efficient strategies to solve this problem. Herein, for the first time we designed a porphyrin-involved benzene-1,3,5-tricarboxamide dendrimer (Por-BTA) as a multifunctional interface material between the interface of the perovskite and the hole-transporting layer (spiro-OMeTAD) for the surface passivation of perovskite films. The results suggested that Por-BTA not only efficiently passivated the perovskite surface defects via the coordination of the exposed Pb2+ with the carbonyl unit and basic sites of pyrrole units in Por-BTA but also improved the interface contact and the charge transfer between the perovskite and spiro-OMeTAD ascribed to the strong intermolecular π–π stacking of Por-BTA. It was shown that the PSC devices with the Por-BTA treatment exhibited improved power conversion efficiency with the champion of 22.30% achieved (21.30% for the control devices), which is mainly attributed to the increased short-circuit current density and fill factor. Interestingly, the stability of moisture for the Por-BTA-treated device was also enhanced compared to those without the Por-BTA treatment. This work presents a promising direction toward the design of multifunctional organic molecules as the interface materials to improve the cell performance of PSCs.

Street vitality is associated with a comfortable human-based public environment and urban sustainability. In most current studies, street vitality is assessed considering single or multi factors; however, the impact of time dimension is ignored. This study selects nine different year-built streets in old, main, and new urban areas, in Nanjing, China, proposes a framework to assess street vitality considering the different time dimensions and selects the following factors: street form, including building density, continuity, and height-width; street business type, including store density, function density, and permeation rate; and street accessibility, including location, the number of entrances/exits, transportation, and walkability. After calculating the values of the subfactors, a ranking method was applied to assign the ranking of impact of all factors for a comprehensive analysis. The results showed that Pipa Street, Wufu Street in a main urban area, and Hongmiao Street had the highest street vitality and the highest rankings of almost all the factors. Street vitality in different periods demonstrated that street vitality in new urban areas is lower compared with old and main urban areas.features to present the vitality of urban streets. Jacobs [10] also attempted to find desirable street forms to provide a reference for the design of such urban spaces.Extensive research studies have investigated the correlations between transportation, road type, car parking, pedestrian environment, and street vitality, respectively. It is vital to design suitable streets by creating a safe and comfortable environment [11][12][13]. Boer [14] suggested reducing the speed limit of cars to give pedestrians priority. Ikioda [15] explored the impact of road construction on market and street traders in urban environments, and Calanis et al. [16] analyzed the road safety of people on the street while considering urban road types and traffic. For street car parking, Ajeng and Gim [17] studied on-street car parking issues and analyzed the differentiation between car parking duration and demand on streets in Yogyakarta City, Indonesia. Park et al. [18] analyzed the impact of on-street car parking on the thermal environment of streets for pedestrians according to Korea's green parking project. For the pedestrian environment, Kang also applied multilevel regression models to identify the positive effects of street facilities, such as stores, cultural issues, local street networks on walking volume, and so forth [19].The built environment is also important for street vitality [20,21]. Park et al. [22] applied a multilayer mean radiant temperature model for pedestrians on streets according to the built environment. Sung et al. [23] identified the association of the physical environment with the activity on streets in Seoul City. Lee et al. [24] investigated urban heat island environment cooling with the use of water spray systems in urban street canyons. Lee [25] analyzed the thermal characteristics of streets using a thermal imaging came...