Electrosynthesis, Characterization and Optical Sensing Application of Amino Acid Functionalized Polyfluorene
An amino acid side chain functionalized polyfluorene derivative poly[N-(9-fluorenylmethoxycarbonyl)-glycine] (P9FG) was facilely electrosynthesized and characterized, and the structure, properties and optical sensing application of the obtained polymer were described and discussed. The electropolymerization occurred at C2 and C7 positions of fluorene units, and amino acid side chain groups were not cleaved from polyfluorene backbone in mixed electrolytes of boron trifluoride diethyl etherate and dichloromethane. Thermal analysis demonstrated good thermal stability of P9FG. Fluorescent spectra indicated that P9FG was a good blue light emitting material that could be employed as optical sensors. The soluble P9FG as a turn-off fluorescent sensor could realize the detection of Fe3+, Cu2+ and Cr2O72-, respectively. In addition, P9FG as a turn-off ultraviolet sensor could realize the detection of Cu2+ while as turn-on ultraviolet sensors could also realize the determination of Fe3+ and Cr2O72-, respectively. All results indicate that P9FG is a promising candidate for optical sensing.
Enhanced Mechanics in Injection Molded Isotactic Polypropylene/Polypropylene Random Copolymer Blends via Introducing Network-like Crystal Structure
The crystallization behavior, rheological behavior, mechanical properties and microstructures of injection molded isotactic polypropylene (iPP), polypropylene random copolymer (co-PP) and iPP/co-PP blends were investigated. Differential scanning calorimetry (DSC) and dynamic rheological analysis illustrated that iPP and co-PP were compatible in the blends and co-PP uniformly dispersed in the iPP phase. Polarizing optical microscope (POM) was adopted to observe the crystal size and morphology evolution. The results of mechanical properties and scanning electron microscopy (SEM) indicated that the crystal size of iPP in iPP/co-PP blends (10 wt% co-PP + 90 wt% iPP and 30 wt% co-PP + 70 wt% iPP) radically decreased after the incorporation of co-PP. During crystallization, the molecular chain segments of co-PP could penetrate iPP spherulites and form a network-like crystalline structure. The network-like crystal structure could effectively transmit stress and consume more energy to overcome intermolecular forces to resist stretching. In this way, the strength would improve to a certain degree. The impact fracture mechanism of iPP/co-PP blends is quasi ductile fracture by multiple crazes. Our work discovered that the blends containing 10 wt% and 30 wt% of co-PP exhibited prominent toughness and reinforcement.
Isotactic polypropylene (iPP) samples obtained by pressure vibration injection molding (PVIM) and conventional injection molding (CIM) were studied by polarized-light microscopy (PLM), respectively. It was found that the alternating bright and dark banded spherulites were generated in the transitional region of PVIM parts. It is the first time that the banded spherulites of isotactic polypropylene were observed in polymer processing. What's more, the banded spherulites were proved to be constituted of a-form crystal by hot stage polarized-light microscopy (HT-PLM) and wide angle X-ray diffraction (WAXD). Morphology of the banded spherulites was also studied by scaning electronical microscopy (SEM).
This work focuses on the interaction between polymeric micelles with different charged surfaces and cancer cells in order to study the influence of surface charge on the in vitro cellular uptake efficiency. The amphiphilic diblock copolymers poly(-caprolactone)-b-poly(ethylene oxide) (PCL-b-PEO) with different functional groups at the end of hydrophilic block were synthesized. The functional groups endue the micelles with different charges on the surfaces. The cellular uptake of micelles to T-24 cells (human bladder tumor cells), HepG2 cells (human liver hepatocellular carcinoma cell line) and Hela cells (human epithelial cervical cancer cells) was studied by means of flow cytometer and confocal laser scanning microscopy. The results indicate that the surface charges showed great influence on zeta potential of micelles at different pH values. The in vitro cellular uptake efficiency of micelles with different charged surfaces demonstrated different cellular uptake patterns to three kinds of cancer cells.
The mechanical properties and phase morphologies of cis-1,4-butadiene rubber (BR) blended with polyethylene (PE) at different blend ratios were studied. The tensile test results show that the PE exhibits excellent reinforcing capabilities towards BR. Blending BR with PE results in a remarkable enhancement of tensile strength, modulus and the elongation at break simultaneously. An increment of tensile strength from 1.11 MPa to 16.26 MPa was achieved by incorporation of 40 wt% PE in the blends. The modulus and elongation at break of 40/60 PE/BR blends are also about 5 times higher than those of the pure BR treated under exactly the same conditions. The tear test indicates that the tear strength also increases with the increase of PE content. It reaches 58.38 MPa for the 40/60 PE/BR blend, which is approximately 10 times higher than that of the pure BR. Morphological study demonstrates that the PE forms elongated microdomains finely dispersed in the BR matrix when its content is over 30 wt%, which corresponds to the remarkably enhanced mechanical properties. According to the results, reinforcement mechanism of PE toward BR dependent on the microstructure has been discussed and two different mechanisms have been proposed.
Microwave-assisted One-pot Three-component Polymerization of Alkynes, Aldehydes and Amines toward Amino-functionalized Optoelectronic Polymers
We present a microwave-assisted one-pot polymerization with three-components of alkynes, aldehydes and amines for the synthesis of new amino-functionalized optoelectronic polymers. The polymerization of diynes (1a-1c), dialdehydes (2a and 2b) and dibenzylamine catalyzed by InCl3 was carried out smoothly within 1 h under microwave radiation, yielding four soluble polymers with high molecular weights. The resulting polymers P1 and P2 could be easily dissolved in alcohol and thus utilized as the cathode interlayer for polymer solar cells (PSCs). Compared with the control device, the PSCs with P1 and P2 as the cathode interlayer and PTB7-Th:PC71BM as the photoactive layer exhibited significantly higher power conversion efficiencies (PCEs) of 9.49% and 9.16%, respectively. These results suggest that this polycoupling reaction is an efficient approach to construct three-component polymers for the practical applications.
Synergic Enhancement of High-density Polyethylene through Ultrahigh Molecular Weight Polyethylene and Multi-flow Vibration Injection Molding: A Facile Fabrication with Potential Industrial Prospects
General-purpose plastics with high strength and toughness have been in great demand for structural engineering applications. To achieve the reinforcement and broaden the application scope of high-density polyethylene (HDPE), multi-flow vibration injection molding (MFVIM) and ultrahigh molecular weight polyethylene (UHMWPE) are synergistically employed in this work. Herein, the MFVIM has better shear layer control ability and higher fabrication advantage for complex parts than other analogous novel injection molding technologies reported. The reinforcing effect of various filling times and UHMWPE contents as well as the corresponding microstructure evolution are investigated. When 5 wt% UHMWPE is added, MFVIM process with six flow times thickens the shear layer to the whole thickness. The tensile strength and modulus increase to 2.14 and 1.39 times, respectively, compared to neat HDPE on the premise of remaining 70% impact strength. Structural characterizations indicate that the enhancement is attributed to the improvement of shish-kebab content and lamellae compactness, as well as related to the corresponding size distributions of undissolved UHMWPE particles. This novel injection molding technology with great industrial prospects provides a facile and effective strategy to broaden the engineering applications of HDPE materials. Besides, excessive UHMWPE may impair the synergistic enhancement effect, which is also reasonably explained.
Tunable Cis-cisoid Helical Conformation of Poly(3,5-disubstibuted phenylacetylene)s Stabilized by n→π* Interaction
A series of novel cis poly(phenylacetylene)s (PPAs) substituted at meta-position(s) by two alkoxycarbonyl pendants, i.e., sP-Me-C8/rP-Me-C8 , P-Me-C12 , sP-Et-C4 , sP-2C4 and sP-Oct-C4 , were synthesized under the catalysis of [Rh(nbd)Cl]2 (nbd = norbornadiene). The dependence of elongation, screw sense, and stimuli response of helical polyene backbone on the structure of pendant, solvent, and temperature was systematically investigated in both solution and solid states. Because of n→π* interaction between vicinal carbonyl groups, sP-Me-C8/rP-Me-C8 could adopt contracted cis-cisoid helix in THF, toluene, CH2Cl2, and CHCl3. Such an intramolecular interaction was sensitive to the hydrogen bond donating ability of solvent and temperature, but insensitive to the dielectric constant and polarity of solvent. In poly(3-methoxycarbonyl-5-alkoxycarbonylphenylacetylene), the longer the chiral alkyl chain was, the easier the stable cis-cisoid helix could be achieved. However, when the methoxycarbonyl was changed to ethoxycarbonyl, sec-butyloxycarbonyl, and octyloxycarbonyl pendant groups, only cis-transoid helix was obtained at room temperature due to the increased steric hindrance. Moreover, lowering temperature was found to facilitate the stabilization of n→π* interactions, and reversible temperature-dependent stereomutations were achieved in sP-Me-C8 and sP-Et-C4 depending on the solvent where they were dissolved. These results suggested that the long alkyl chain, small pendant size, and lower temperature favored the stabilization of intramolecular n→π* interactions and the formation of contracted, cis-cisoid helices for poly(3,5-diester substituted phenylacetylene)s.
A novel switchable luminescent thermometer based on thermo-responsive triblock copolymer poly(ethylene glycol)-b-poly(acrylamide-co-acrylonitrile-co-dimethylaminoethylmethacrylate) (PEO113-b-P(AAm264-co-AN112-co-DMA8)) and Eu-containing polyoxometalate (Eu-POM) was successfully constructed. The copolymer synthesized by RAFT exhibited a linear response to temperature variations in aqueous media, which was quite different from the uncharged copolymer P(AAm-co-AN) having a specific upper critical solution temperature (UCST). Eu-POM was surrounded around thermo-responsive blocks through electrostatic interactions, and its luminescence could be finely tuned due to the sensitivity of copolymer to the temperature variation. In cold water, POMs were trapped in highly hydrophobic cores, exhibiting an intense emission. With the upraising of temperature, the emission intensity presented a gradual decrease and showed a linear correlation with temperature. When the complex solution cooled down, the luminescence could also be perfectly restored. This temperature-luminescence correlation could be held for numerous trials, showing a potential application in thermometer.