Tailored Degradation and Dye Release from Poly(ester amides)

Poly(ester amides) based on L-valine and adipic acid with different aliphatic and aromatic diols were synthesized by interfacial polymerization. Four different diols such as ethylene glycol, 1,5-pentanediol, resorcinol, and catechol were used to systematically vary the chain lengths and position of the hydroxyl groups. The chemical structures, thermal properties, degradation, and dye release of these polymers were investigated. This study demonstrates that the release kinetics can be tailored through the control of the chain length of the diol and the position of the hydroxyl groups. These findings have important implications for designing biodegradable polymers for tailored release.     

A comparative study of new linear and hyperbranched polyurethanes built up from a synthesized isocyanate-terminated polyester/urethane

In the present study, the effects of architecture and structural building blocks of the polyurethane chains on their properties were studied. New linear and hyperbranched polyurethanes (LPU and HPU) were prepared via A2 + B2 and A2 + B3 methodologies, respectively. Polyethylene glycol (PEG-1000) and castor oil (CO) were used as bi- and trifunctional monomers (B2 and B3), respectively. However, A2 monomers were synthesized by the reaction between ethylene glycol (EG) with terephthaloyl chloride (TPC) and reacting the product with excess toluene diisocyanate (TDI) to produce isocyanate-terminated PU (NCO-PU). NCO-PU was reacted with PEG to synthesize LPU; however, its reaction with CO synthesized HPU. NCO-PU, LPU and HPU were characterized by FTIR, H-NMR, GPC, TEM, TGA, DSC and XRD. The prepared PUs were applied as coatings and their physical, chemical and mechanical properties were investigated. The results showed that the degree of branching of HPU was 79%. No phase separation was observed in NCO-PU as indicated by its DSC curve. However, two phases are detected in HPU and LPU that represent to the hard and soft segments. NCO-PU displayed the highest crystallinity index (CrI = 89.26%). However, the high degree of branching in HPU led to lower CrI than LPU. The lack of entanglements in HPU led to its slightly lower solution viscosity than LPU. TEM images showed spherical PU nano-particles. The surface of HPU coating showed the highest gloss which is due to its low degree of crystallinity. HPU and LPU exhibited excellent chemical resistivity.     

Strong Reactivity Enhancement through Molecular Traffic Control in Zeolites

In the past, the investigation of catalytic reactivity enhancement through molecular traffic control (MTC) by means of dynamical Monte Carlo simulations of catalysis was initiated in simple, idealized zeolite channel networks. These results are reviewed here and, emphasizing more recent work, the conditions of reactivity enhancement through MTC are examined for a realistic channel topology based on the pore structure of the zeolite TNU‐9. For a wide range of reaction rates a very strong MTC effect can be found that increases with grain size. This effect is argued to be a generic feature of a certain class of zeolite pore topologies.     

0.40% Bipolar Strain in Lead Free BNT–KNN System Modified with Li,Ta and Sb

In this work we demonstrate a large electric field‐induced bipolar strain ~0.40% in Li, Ta and Sb modified BNT–KNN ((1?x) Bi_0.5Na_0.5TiO₃–xK_0.47Na_0.47Li_0.06 Nb_0.74Sb_0.06Ta_0.2O₃) system. The morphotropic phase boundary (MPB) of the system between rhombohedral and tetragonal phases lies in the range 0.02 ≤ x ≤ 0.06, beyond which all compositions (up to x < 0.15) were found to be tetragonal. A clear trade‐off between the large strain values and achievable d₃₃, k_p for a particular composition was noted. It is shown that while for x = 0.03, d₃₃ 169 pC/N, k_p 49% and strain ~0.13% were obtained, for x = 0.08 with 0.40% strain, d₃₃ and k_p values decreased drastically.     

The fast reaction asymptote of the coalescence-redispersion model

The coalescence-redispersion (CRD) model is examined in the fast chemistry limit for the single bimolecular reaction A+B M R and the series parallel reactions A+B M R;B+R M S occurring in a plug flow reactor with unmixed feed streams. For the single bimolecular reaction it is shown that in this limit the CRD model is asymptotically equivalent to the 3E fast closure as t M 0. For the series parallel reactions the CRD model predictions tend to be bracketed by the 3E slow and fast closure formulations. Representative results are presented for the variance decay of the individual reactants, and it is seen that even in the fast reaction limit where mixing is controlling, the shape of the feed stream PDFs has negligible influence on the progress of the reaction.     

Significant Decline in Galactomannan Signal during Storage of Clinical Serum Samples

Galactomannan (GM) is widely used for detection of invasive aspergillosis in high-risk haemato-oncology patients. Recent publications have reported a lack of repeatability of GM detection. The objective of this retrospective study was to assess the repeatability of GM levels during storage of clinical samples. In a GM screening strategy, positive sera were repeat tested as per manufacturer’s recommendations. Short-term (ST) storage of samples was at +4 °C while long-term (LT) storage was at −80 °C. Bronchoalveolar (BAL) fluid was also repeating tested after ST storage and LT storage. Wilcoxon Signed Ranks Test was employed to assess the repeatability of GM levels. In a subset of 14 GM positive sera, repeat testing was performed on both the original serum and ethylenediaminetetraacetic acid (EDTA) pre-treated sample. There was a significant reduction in GM signals on repeat testing following ST storage (median GM index: 0.65 vs. 0.19; p < 0.001) and LT storage (median GM index: 0.56 vs. 0.10; p < 0.001) of serum samples. Of samples that were initially GM positive, an average GM index reduction of 50% was seen, with approximately two-thirds becoming GM negative on repeat testing of the same sample. In contrast, GM signal loss was not seen on repeat testing of BAL fluid following ST or LT storage. When GM positive serum samples were repeat tested using EDTA pre-treated serum from the first step of the testing protocol, all samples remained GM positive. In contrast, when the same samples were repeat tested from the original collected serum, 9 samples (64%) became GM negative. The significant reduction in GM signals during ST and LT storage of serum samples has implications for clinical management. Although the reasons for GM decline are unknown, they occur prior to the EDTA pre-treatment stage, indicating that the time from phlebotomy to testing should be minimized. BAL fluid GM index values remain stable.     

Vinylogous Organocatalytic Triple Cascade Reaction: Forging Six Stereocenters in Complex Spiro‐Oxindolic Cyclohexanes

We report a triple vinylogous cascade reaction, yielding valuable spiro‐oxindolic cyclohexane derivatives. The three‐component domino process proceeds by way of a catalyzed Michael/1,6‐addition/vinylogous aldol sequence affording the products with six stereogenic centers and very high control over the stereochemistry. The chemistry is based on a rare example of asymmetric 1,6‐addition to linear 2,4‐dienals proceeding with complete δ‐site selectivity. Key to the reaction development was a directing group positioned at the β‐dienal position, which was essential for achieving highly predictable reaction outcomes.

     

The beneficial effect of small amount of water in the ambient temperature atom transfer radical homo and block co-polymerization of methacrylates

ATRP of several methacrylates viz. methyl methacrylate (MMA), ethyl methacrylate (EMA), n-butyl methacrylate (nBMA), t-butyl methacrylate (tBMA), benzyl methacrylate (BzMA) and (N,N-dimethylamino)ethyl methacrylate (DMAEMA) has been studied in neat as well as aqueous (up to 12 vol% water) acetone at 35 °C using CuCl/bipyridine (bpy) catalyst and ethyl 2-bromoisobutyrate as the initiator. Addition of water significantly enhances the rate of polymerization without losing control. Unlike CuCl/bpy the CuBr/bpy catalyst gives poor control which is attributed to the lower solubility and consequent heterogeneity in the latter case. Of the other ligands used with the CuCl catalyst viz. o-phenanthroline (o-phen), 1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA), 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA), Me₆TREN only o-phen offers reasonably good control. The CuCl/bpy catalyst system has been used also in preparing some di- and tri-block copolymers with reasonably low polydispersity index (PDI) at ambient temperature (35 °C) using aqueous acetone as the solvent. The following block copolymers have been prepared PMMA-tBMA, PMMA-b-tBMA-b-MMA, PMMA-DMAEMA, by this method.     

Morphological,Mechanical Property Analysis and Comparative Study over Structural Properties of CVD TiN Film Grown under Different Substrate Temperature in Nitrogen Gas Atmosphere

Silicon - Titanium Nitride (TiN) thin films were deposited by thermal chemical vapor deposition process (CVD) over Si (100) substrate under different substrate temperatures. Morphological,...     

Host-Assisted Delivery of a Model Drug to Genomic DNA: Key Information from Ultrafast Spectroscopy and in silico Study

Drug delivery to a target without adverse effects is one of the major criteria for clinical use. Herein, we have made an attempt to explore the delivery efficacy of SDS surfactant in a monomer and micellar stage during the delivery of the model drug, Toluidine Blue (TB) from the micellar cavity to DNA. Molecular recognition of pre-micellar SDS encapsulated TB with DNA occurs at a rate constant of k₁ ∼652 s⁻¹. However, no significant release of encapsulated TB at micellar concentration was observed within the experimental time frame. This originated from the higher binding affinity of TB towards the nano-cavity of SDS at micellar concentration which does not allow the delivery of TB from the nano-cavity of SDS micelles to DNA. Thus, molecular recognition controls the extent of DNA recognition by TB which in turn modulates the rate of delivery of TB from SDS in a concentration-dependent manner.