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The assembling behavior of four thiophenecontaining conjugated polymers, regioregular poly(3-hexythiophene) (rr-P3HT), poly(3,3-didodecylquaterthiophene) (PQT-12), poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno-[3,2-b]thiophene) (PBTTT-14), and poly(2,5-bis(3-tetradecylthiophen-2-yl)thiophen-2-yl)thiophen-2-ylthiazolo[5,4-d]thiazole) (PTzQT-14), on carbon nanotubes was investigated through microscopic studies of nanowire formation and theoretical simulation. It is found that polymer backbone rigidity and shape influence the attachment mode on carbon nanotubes. rr-P3HT and PQT-12 have a zigzag backbone structure that allows a thermodynamically stable coaxial attachment on CNTs, providing an ordered growth front for the nanowire formation. In contrast, fused rings in PTzQT-14 and PBTTT-14 create a stair-step like backbone structure that causes a kinetically controlled wrapping conformation on CNTs, generating a twisted growth front that hinders the nanowire formation. In addition, the rigidity of polymer backbone influences the wrapping mode. Polymers with more flexible backbones (i.e., PBTTT-14) would take a dense irregular wrapping mode on CNTs. The CNT diameter plays an important role in the nanowire formation when CPs attach to the CNT in the wrapping mode. Larger nanotubes with smaller surface curvature provides a less twisted polymer growth front, allowing the formation of CPNWs.

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Photo-retro-Diels-Alder (PrDA) reactions of a variety of Diels-Alder (DA) adducts were studied. Experimental results showed that the photoreactivity (quantum yield) depends on the electron-donating ability of the diene component and the electron-withdrawing ability of the dienophile component. The mechanism was studied by trapping the reaction intermediate, O(2) quenching, time-resolved absorption, and fluorescence spectroscopy. All the results support a mechanism that involves a charge-separated intermediate generated from a singlet excited state. The PrDA reaction may find applications in photoresponsive materials, photolithography, drug delivery, and mechanistic research.

The object of this study is to investigate the feasibility of ball-milled graphene oxide nanoflakes (GONFs) produced by a mechanochemical process as an additive in Ordinary Portland Cement (OPC)-based paste and concrete. Different percentages of GONFs (0.01-1 wt. %) were added in OPC paste mix to find the optimum content of GONF in GONF-combined cement composites. To investigate the effect of the changes in the mix design on OPC paste, two mix design methods were employed: (1) Dry-mix, where GONFs and OPC powders are mixed prior to paste formation and (2) Wet-mix, where sonicated GONFs solution is used as the pour water with OPC paste mix. Data from mechanical tests (compressive and flexural tests) showed that OPC paste incorporating 0.05% GONF resulted in the highest strength for OPC paste. The results of strength tests indicated that Dry-mix is competitive as compared with Wet-mix. Scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) was used to identify GONFs inside products of cement hydration. To explore the practicality of using GONF in concrete, concrete specimens were made, cured and tested with different percentages of dry-mixed GONFs (0.01-0.1 wt. %). The result of strength test showed that GONF improves the compressive and flexural strengths of concrete around 15% with 0.01 wt. % GONF.