Preparation of fluorescent hyperbranched polymer materials by end-capping approach

Two kinds of novel fluorescent hyperbranched polymers were synthesized by the end-capping approach. The fluorescent hyperbranched polyether (FPEOTM) was obtained by end capping the hyperbranched poly(hydroxyl ether) (PEOTM) with guest molecules N,N-dimethylaminobenzaldehyde (DMABA). In addition, in the presence of triethylamine, the hyperbranched polysulfone-amine with terminal double bonds (HPSA) was synthesized by polyaddition of a new AB2 type monomer (SAP, sulfone amine piperazine) at 40℃ for 60 h in chloroform solution. Then the fluorescent hyperbranched polysulfone-amine (FHPSA) was prepared by addition of guest molecules N,N-dimethylaminoanilines (DMAA) with the terminal double bonds of HPSA. The two resulting polymers fluoresce yellow-green color in both solid and solution states. The maximum emission wavelength is (460 ±10) nm and (470±10) nm, respectively. A novel 'complex quenching effect' for hyperbranched polymer was observed. The fluorescence can be quenched by transition metal

The effect of end-capping groups in A-D-A type non-fullerene acceptors on device performance of organic solar cells

A series of novel wide bandgap small molecules(IFT-ECA, IFT-M, IFT-TH and IFT-IC) based on the A-D-A structure with indenofluorene core, thiophene bridge, and different electron-deficient end-capping groups, were synthesized and used as non-fullerene acceptors in organic solar cells. The influences of end-capping groups on the device performance were studied.The four materials exhibited different physical and chemical properties due to the variation of end-capping groups, which further affect the exciton dissociation, charge transport, morphology of the bulk-heterojunction films and device performance. Among them, IFT-IC-based device delivered the best power conversion efficiency of 7.16% due to proper nano-scale phase separation morphology and high electron mobility, while the devices based on the other acceptors achieved lower device performance(4.14% for IFT-TH, <1% for IFT-ECA and IFT-M). Our results indicate the importance of choosing suitable electron-withdrawing groups to construct high-performance non-fullerene acceptors based on A-D-A motif.

Effect of block length on the self-assembly of end-capping perfluoroalkyl moieties on the polymer surface

Most research on copolymers with fluorinated monomers has focused on the relationship between fluorinated monomer content and the corresponding surface structure. However,the influence of the non-fluorinated block on the surface structure of the copolymer film is unknown. Various molecular weight poly(butyl methacrylates) (PBMA) end-capped with 2-perfluorooctylethyl methacrylate (FMA) units (PBMA-ec-FMA) have been synthesized by atom transfer radical polymerization (ATRP). The effect of the PBMA block length on the surface structure and properties of the polymers both in the solid state and in solution was investigated using various techniques. X-ray photoelectron spectroscopy (XPS),sum frequency generation (SFG) vibrational spectroscopy and X-ray diffraction (XRD) analyses indicated that longer PBMA blocks enhanced both the enrichment of the fluorinated moieties and the order of the packing orientation of the perfluoroalkyl side chains on the surface. This enhancement was attributed mainly to the molecular aggregate structure of the end-capped polymers with long PBMA blocks in the solution and to the interfacial structure at the air/liquid interface,which favors the -(CF2)7CF3 moieties self-assembling on the polymer surface during film formation. This observation suggests that the polyacrylate block structure in fluorinated diblock copolymers,in addition to the fluorinated monomer content,plays an important role in structure formation on the solid surface.

A New Implant for Transfemoral Amputation: Improved Gait and Comfort

Introduction: Transfemoral amputation results in a prosthesis which bears weight on the ischium. Gait disturbance, lack of an end-bearing stump and discomfort in the groin from the socket even while sitting, are important issues. Methods: This is a pilot report of an ongoing randomized blind clinical trial of a new intramedullary implant post transfemoral amputation. Here, we describe a single case illustrating the surgical technique and clinical outcome of a dysfunctional post-traumatic transfemoral amputation addressed with this implant. Clinical gait analysis, SF-12 and VAS were assessed pre- and post-intervention at 6 months of follow-up. Results: An improved stump control is accomplished by means of myoplasty and myodesis through an end-cap. Stride width improved from 0.21 m pre-op to 0.13 m post-op, and more symmetrical stride length (△0.21 m pre-op vs. △0.06 m post-op) was noted, indicating improved gait quality and stability. Gait velocity increased (0.51 ± 0.04 m/s pre-op vs. 0.64 ± 0.02 m/s post-op). Conclusion: This technique reveals improvements in gait parameters in a transfemoral amputee treated with a new procedure. Improved prosthesis control, sitting comfort, greater hip range of motion, better gait stability, and enhanced walking abilities were noted.

An end-capped strategy for crystalline polymer donor to improve the photovoltaic performance of non-fullerene solar cells

The effects of end-capped modifications of a polymer donor with high molecular weight on non-fullerene solar cells are largely ignored,even if the chain-end-functionalized method of conjugated polymers is an effective strategy in modulating polymeric optical-electronic properties.In this study,we design and synthesize an end-capped polymer,PM6TPO,via a reaction with the parent polymer PM6.Meanwhile,the conventional detection methods of X-ray photoelectron spectroscopy(XPS),matrix-assisted laser desorption/ionization time-of-flight(MALDI-TOF),and ^(1)H nuclear magnetic resonance(^(1)H NMR) were replaced by simple solution-based inductively coupled plasma-mass spectrometry(ICP-MS) to evaluate the end-capped efficacy of PM6TPO.By introducing end-capped groups on a high molecular weight polymer donor,we could finely tune the aggregated behavior,strengthen the miscibility between the donor and acceptor without sacrificing the strong aggregated properties,and reduce the non-radiative recombination with a lower energy loss.Therefore,the PM6TPO-based organic solar cell(OSC)realized a higher open-circuit voltage of 0.843 V and PCE of 17.26% than that of the non-end-capped parent polymer,PM6(0.824 V and 16.21%,respectively).This work not only provides a straightforward method for verifying the end-capped efficacy of a high molecular weight polymer but also indicates a new research direction for improving the photovoltaic performance of non-fullerene-based solar cells.

Highly efficient and stable coupling of kilowatt-level continuous wave laser into hollow-core fibers

Fiber gas lasers based on gas-filled hollow-core fibers(HCFs)perfectly combine the advantages of fiber lasers and gas lasers and have obtained fast development in the past years.However,stable and efficient coupling of high-power pump lasers into the HCFs is one of the key problems to be solved.In this paper,we study the coupling of high-power continuous wave fiber lasers into anti-resonant HCFs through an end-cap.By optimizing the splicing parameters,a maximum laser power of 1167 W was injected into the 1-m-long HCFs,and 1021W was obtained at the output end,giving a total transmission efficiency of〜87.5%.A more than 1 h test showed the stability of such a coupling method.Meanwhile,the laser beam quality was well maintained.This work opens new opportunities for stable and highly efficient coupling of high-power lasers into HCFs,which is significant for its applications in many other fields besides high-power fiber gas lasers,such as high-power laser delivering.

CHARACTERIZATION AND THERMAL STABILITY OF PMR POLYIMIDES USING 7-OXA-BICYCLO[2,2,l]HEPT-5-ENE-2,3-DICARBOXYLIC ANHYDRIDE AS END CAPS

An anhydride monomer containing ether oxide bridge, 7-oxa-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic anhydride （ONA）, was successfully synthesized by Diels-Alder reaction of furan and maleic anhydride. The ONA was also studied as an end-cap for the polymerization of monomer reactant （PMR） type polyimides. Three molecular weight levels of the ONA end-capped PMR resins were evaluated. The effects of process conditions of these novel PMR resins on thermal and mechanical properties were investigated. It was demonstrated that the imidized prepolymers using the end-cap have good processability, and the cured polyimide specimens exhibited good thermal stability. The initial decomposition temperature, Td （ca. 580℃） and glass transition temperature, Tg （330℃） of the novel resin （PI-20）, prepared trader optimum process conditions, compare favorably with the Td （ca. 620℃） and Tg （ca. 348℃） of the state-of-the-art resin （PI＇-20）, respectively.

Preparation of polymer nanocomposites with enhanced mechanical properties using hybrid of graphene and partially wrapped multi-wall carbon nanotube as nanofiller

Triblock copolymer of poly（p-dioxanone） and polyethylene glycol end-capped with pyrene moieties（（Py-PPDO）_2-b-PEG） was synthesized and used as modifier for multi-wall carbon nanotubes（MWCNTs）.Nano-aggregates（（Py-PPDO）_2-b-PEG@MWCNTs） with shish-kebab like partially wrapped morphology and very good stability were obtained by incorporating the copolymer with MWCNTs.The bare MWCNT sections of（Py-PPDO）_2-b-PEG@MWCNTs were able to induce n-n interactions with graphene（GE） and resulted in a novel GE/（Py-PPDO）_2-b-PEG@MWCNTs hybrid.The dispersity of GE in solution or polymer matrix was therefore greatly improved.The PCL nanocomposite films using GE/（Py-PPDO）_2-bPEG@MWCNTs as hybrid nanofiller exhibited obviously improved mechanical properties especially at very low hybrid nanofiller content.The influence of the nanofiller content and feed ratio of GE/MWCNTs on the mechanical properties of composites films was evaluated.When the feed ratio of GE to MWCNTs is 2：8 and the total loading of nanofiller is only 0.01 wt%,the tensile strength of the composite film increased by 163%and the elongation at break increased by 17% compared to those of neat PCL These results can be attributed to fine dispersion of the nanofillers in PCL matrix and the hybrid interactions between GE and MWCNTs.Therefore,this work provides a novel method for preparing polymer nanocomposites with high mechanical performance and low nanofiller loading.