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We demonstrate a scanning electron nanobeam diffraction technique that can be used for mapping the size and distribution of nanoscale crystalline regions in a polymer blend. In addition, it can map the relative orientation of crystallites and the degree of crystallinity of the material. The model polymer blend is a 50:50w/w mixture of semicrystalline poly(3-hexylthiophene-2,5-diyl) (P3HT) and amorphous polystyrene (PS). The technique uses a scanning electron beam to raster across the sample and acquires a diffraction image at each probe position. Through image alignment and filtering, the diffraction image dataset enables mapping of the crystalline regions within the scanned area and construction of an orientation map.

Synthesis and photovoltaic properties of two donor−acceptor polymers containing benzodithiophene with 3,3′,5-trihexylbithienyl substituents are reported. Benzo[c]-[1,2,5]thiadiazole and 5-hexylthieno [3,4-c]pyrrole-4,6-dione were used as acceptor building blocks for the synthesis of donor−acceptor polymers. The photovoltaic properties of the synthesized donor−acceptor polymers were investigated in bulk heterojunction solar cells with [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) acceptor. ■ INTRODUCTIONBenzodithiophene semiconducting polymers have garnered considerable interest in the past few years due to their good performances in both organic field-effect transistors and polymeric solar cells. 1,2 In addition to having a planar backbone, the benzodithiophene core offers the flexibility of attaching different substituents on the central benzene core to fine-tune the energy levels of the polymer. 2−4 Various research groups have exploited this property and attached different substituents such as alkyl, alkoxy, and thioalkyl to the benzene core of benzodithiophene. 2,3,5−9 Our group reported the synthesis and electronic properties of benzodithiophene polymers with alkyl phenylethynyl substituents. 10 More recently, the Yang group reported the synthesis of donor−acceptor polymers containing benzodithiophene with a conjugated thienyl substituent. 11 Huo showed that replacing the alkoxy with alkylthienyl substituents on the BDT core increases the thermal stability, gives broader absorption spectra, lowers the HOMO and LUMO energy levels, and improves the photovoltaic properties of the polymers. 12−14 Furthermore, the attachment of thienyl substituents to the BDT can result in increasing the solubility of the polymer as it provides the ability to attach a larger number of alkyl substituents on the thiophene ring. 15 For example, Cao attached four alkyl chains on the BDT building block which improved the solubility of the resulting polymer. 15 Recent reports have shown that benzodithiophene semiconducting polymers displayed power conversion efficiencies (PCE) in excess of 7% in bulk heterojunction (BHJ) solar cells. 16,17 Donor−acceptor polymers with lower band gaps are highly desirable for organic solar cell applications. Additionally, the ability to improve the open-circuit voltage (V oc ) has attracted much attention. Since the V oc of a BHJ solar cell is directly proportional to the difference between the HOMO of the donor and the LUMO of the acceptor, lowering the HOMO level of the donor polymer will be a crucial factor in enhancing the V oc . 18 Moreover, a donor−acceptor copolymer with a deeper HOMO level will enhance the oxidative stability of the polymer. Hou and co-workers synthesized a donor−acceptor polymer with 5-alkylthiophene-substituted BDT with a deeplying HOMO of −5.3 eV and obtained an air-stable donor polymer that gave a V oc of 0.88 V in bulk heterojunction solar cells. 12 To generate highly soluble semiconducting polymers with higher molecular weight and broader absorption in the visible re...

The new polymerization of carbodiimides using two, simple [bis(triphenylphosphino)aryl]nickel(II) bromide complexes has been discovered to occur in a controlled, living fashion. These initiators are substantially more air and moisture stable compared to their titanium(IV) counterparts making them significantly easier to synthesize, purify, and utilize. The polymerization is initiated via aryl ligand transfer to the electrophilic center carbon of the carbodiimide. Sequential insertions of the carbodiimide π-bond into the nickel−nitrogen amidinate coordination bond propagates the polymer chain in a living chain growth manner as evident by the linear relationship in the plots of percent conversion vs M n , ln ([M] o /[M]) vs time, and monomer: initiator ratio vs M n . The transferred aryl ligand was confirmed to be appended to the terminus of the polymer chain by MALDI−TOF and 19 F NMR. This added control element offers new opportunities to end functionalize rigid-rod, helical polycarbodiimides. This new technique also provides the ability to generate the active Ni(II) initiation sites on potentially any aryl bromide species for the facile incorporation of rod-like, helical polycarbodiimides into such systems as block copolymers, graft copolymer, polymer functionalized surfaces, etc. To demonstrate this, poly(4-bromostyrene) was employed as a polymer-supported aryl bromide source to generate the active [bis(triphenylphosphino)aryl]nickel(II) bromide macroinitiator. The "grafting from" reaction was then carried out upon addition of the chiral (S)-PEMC monomer forming the excess single-handed helical polycarbodiimide appended graft copolymer. The morphology of this novel polymer system was studied using TMAFM, revealing nanofibular aggregation behavior when spin coated from dilute CHCl 3 solutions.

A B S T R A C TPerfluoropolyethers (PFPE) are commercially available non-flammable short chain polymeric liquids. Endfunctionalized PFPE chains solvate lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt and these mixtures can be used as electrolytes for lithium (Li) batteries. Here we synthesize and characterize a new class of solid PFPE electrolytes. The electrolytes are made by either thermal or UV crosslinking PFPE chains with urethane methacrylate end-groups. For the synthesis of thermally crosslinked electrolytes, polyhedral oligomeric silsesquioxane (POSS) with organic acrylopropyl groups was used as crosslinker agent, while for UV cured electrolytes a photoinitiatior was used. We present thermal, morphological, and electrical data of the solid electrolytes. We compare these properties with those of the two parent liquids (PFPE with urethane methacrylate end-groups and POSS with acrylopropyl groups) mixed with LiTFSI. The solubility limit of LiTFSI in the PFPE-based solids is higher than that in the liquids. The conductivity data are analyzed using the Vogel-Tamman-Fulcher equation. The concentration of effective charge carriers is a strong function of the nature of the solvent (solid versus liquid) whereas the activation energy is neither a strong function of the nature of the solvent nor salt concentration.