Janus-type isopropyl groups revealed by 1H-NMR spectra of alkylpyridines with lanthanide shift reagents (LSR)

Two Isomeric pyridines were designed and prepared : 2-isopropyl-4,5,6-trimethyl-(3) and 2-isopropyl-3,4,6-trimethyl-pyridine (7); the latter, with a buttressed isopropyl, leads to much lower induced shifts by Eu(dpm)₃ and Pr(dpm)₃ than the former, owing to the conformation in which the Janus-type iPr group how to the LSR a t-butyl-like face.     

Effect of permodified β‐cyclodextrin on the photophysical properties of poly[2,7‐(9,9‐dioctylfluorene)‐alt‐(5,5′‐bithiophene)] main chain polyrotaxanes

The photophysical properties of two polyrotaxanes ( PFBTh?PSβCD and PFBTh?PMeβCD ) composed of fluorene and bithiophene encapsulated into permodified β‐cyclodextrin cavities have been investigated and compared with those of the reference PFBTh . Rotaxane formation results in improvements of the thermal stability, solubility in common organic solvents, as well as better film forming ability combined with a high transparency. As expected PFBTh and its encapsulated forms absorb at wavelengths beyond 510 nm, and time‐resolved photoluminescence (PL) in solution shows a well‐define vibronic structures with a predominance of the 0‐0 transitions and an energy difference of 0.16 eV. The fluorescence lifetimes follow a monoexponential decay with a value τ = 630 ± 30 ps. Atomic force microscopy, AFM, indicated a tendency of polyrotaxanes to organize into fibers. The advancing contact angles indicated higher surface hydrophobicity and lower surface free‐energy values for polyrotaxanes compared with their unthreaded analogues. The device based on PFBTh?PSβCD: PCBM in a 1/1 w/w ratio under simulated AM 1.5G illumination at 100 mW cm^?2 exhibited improved photovoltaic parameters of cells, resulted in high V_oc (0.68 V), J_sc (1.65 mA cm^?2), FF (31.6%), and PCE (0.35) values, compared with PFBTh or PFBTh?PMeβCD , respectively. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 460–471     

Copolymerization of 2‐hydroxyethyl methacrylate with a comonomer with spiroacetal moiety

The study reports the synthesis of a copolymer based on 2‐hydroxyethyl methacrylate and 3,9‐divinyl‐2,4,8,10‐tetraoxaspiro[5.5]undecane (U) acquired through radical polymerization in the presence of 2,2′‐azobis(2‐methylpropionitrile). The attempt was to have a solid content as high as 10 wt %. The polymerization process was conducted in the presence of a classic ionic surfactant—sodium lauryl sulfate—and comparatively using two variants of protective colloid β‐cyclodextrin and poly(aspartic acid), respectively. The prepared dispersions were characterized from the viewpoint of their hydrodynamic radius, zeta potential, and conductivity evolution during syntheses. The mean particle size and size distribution and zeta potential and conductivity were also evaluated for the synthesized polymeric particles. The compositions of the polymers were confirmed by FTIR and ¹H NMR spectra, and also, the thermal stability of the polymeric compounds was evaluated. SEM and AFM investigations of the polymer morphology are also presented. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and electro‐optical properties of polyfluorene modified with randomly distributed electron‐donor and rotaxane electron‐acceptor structural units in the main chain

Polyfluorene PF?γCD rotaxane copolymer, composed of randomly distributed 9,9‐dioctylfluorene, methyltriphenylamine (electron‐donating) and 9‐dicyanomethylenefluorene complexed with γ‐cyclodextrin (γCD) (electron‐accepting) structural units, has been synthesized by Suzuki cross‐coupling reaction. The chemical structures were proved by FTIR and ¹H NMR spectroscopy. The surface morphology, thermal, optical, electrochemical behavior, and adhesion characteristics of the obtained rotaxane copolymer have been investigated and compared with those of the nonrotaxane counterpart ( PF ). Relatively high fluorescence efficiency, almost identical normalized absorbance maximum in solution and solid‐state of PF?γCD rotaxane copolymer, and a more uniform and smoother surface with lower adhesion forces provides the role of γCD encapsulation on the lower aggregation propensity. PF?γCD and PF copolymers exhibit n‐ and p‐doping processes and blue‐light emission in the film state. The optical and electrochemical band gaps (ΔE_g), as well as the highest occupied molecular orbital/lowest unoccupied molecular orbital positions in an energetic diagram indicate that both copolymers are promising blue‐emitting electroluminescent materials. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Research about transmission of the mechanical vibration done by machine-tools on the group of bones shoulder-neck-head

Different researches have shown that long–term exposure to whole–body vibration can induce different injuries like back pain, injuries of the different part of the body, disturbing the physical and intellectual activities. The resulted diseases could be occasional or could be for ever. Bearing in mind that vibration is applied on the hand or feet, the health rick can be assessed if the forces transmitted in the shoulder during vibration are known. To estimate the forces a biomechanical model has been developed in which the shoulder, neck and head are represented by rigid bodies. The bodies are connected by visco–elastic joint elements. The applied forces are resulted from experimental measurements. To assess the health risk the forces must be divised in two components, an ascendant one and a descendent one. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Geometry of chemically modified silica

The effect of alkyl chain length on adsorbent pore volume and void volume of HPLC columns is described. The results provide evidence that alkyl chains attached on silica surface are densely packed. A correlation of a decrease of pore volume with an increase of the alkyl modifier chain length was found. Effective molecular volume of bonded chains was found to be similar to the molecular volume of corresponding liquid alkanes. An absence of noticeable penetration of acetonitrile, methanol, or tetrahydrofuran molecules between bonded chains at any water-organic eluent composition was found.     

Volume-load capacity in fast-gradient liquid chromatography effect of sample solvent composition and injection volume on chromatographic performance

We studied the effects of sample solvent composition and injection volumes on the chromatographic performance of ODS-bonded silica columns under fast-gradient running conditions. Chromatographic performance is compromised as a function of both sample injection volume and sample solvent strength, with earlier-eluting analytes being much more affected than later-eluting ones. In general, when injecting samples dissolved in a strong solvent, performance was improved by diluting the strong injection solvent and injecting a proportionally larger volume. Volume loading capacity can be increased by using a longer column, or by using a column of equivalent length, but with a larger inner diameter. Data also suggest that sample solvent strength, not viscosity, is responsible for the noted effects.