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81.
Impact of poly(ɛ‐caprolactone) architecture on the thermomechanical and shape memory properties
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Prashant Deshmukh Hyeongho Yoon Seungwan Cho Sook Young Yoon Omkar V. Zore Taeyoon Kim Ildoo Chung Suk‐Kyun Ahn Rajeswari M. Kasi 《Journal of polymer science. Part A, Polymer chemistry》2017,55(20):3424-3433
We report the synthesis of linear‐ and brush‐type poly(?‐caprolactone) (PCL) networks and investigate their thermal, mechanical, and shape memory behavior. Brush‐PCLs are prepared by ring‐opening metathesis polymerization (ROMP) of a norbornenyl‐functionalized ?‐caprolactone macromonomer (MM‐PCL) of different molecular weights. The linear analog, diacrylate end‐functionalized PCL (linear‐PCL), having comparable molecular weight of side chain of brush‐PCL is also synthesized. These polymers are thermally cured by a radical initiator in the presence of poly(ethylene glycol) diacrylate crosslinker. Thermal and linear viscoelastic properties as well as shape memory performance of the resulting PCL networks are investigated, and are significantly impacted by the PCL architecture. Therefore, our work highlights that tailoring macromolecular architecture is useful strategy to manipulate thermal, mechanical, and resulting shape memory properties. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3424–3433 相似文献
82.
The reaction of various alcohols with paraformaldehyde in presence of montmorillonite to give dialkoxymethanes (2a-g) in very good yield is described. 相似文献
83.
Yogita Deshmukh Puja Khare Altafhusain B. Nadaf Dharnidhar Patra 《Journal of Chemometrics》2015,29(12):648-658
2‐Acetyl‐1‐pyrroline (2AP) is known as a principal basmati aroma compound. The present study aims at discriminating rhizobacteria isolated from soils cultivated with basmati and non‐basmati rice for long duration. Volatile profiling was used as marker to discriminate the rhizobacterial isolates. Quantification of 2AP and other volatile compounds (VCs) produced by rhizobacteria was undertaken using HS‐SPME coupled with GC‐MS. Chemometrics tools such as hierarchical cluster analysis (HCA), principle component analysis (PCA) and multi dimensional scaling (MDS) were applied for volatile profiling of different isolates. Results showed significant discrimination of all 2AP producing (AP‐P) and non‐producing rhizobacterial isolates (AP‐NP) on the basis of their VC profile. This was validated by bacterial identification data as well. The frequency distribution for 2AP levels indicates that basmati isolates had higher frequency for 2AP production as compared to non‐basmati control. AP‐P and AP‐NP isolates have different VC profiling pattern irrespective of their origin. These isolates were found belonging to different groups when identified using 16S rDNA sequencing data. Chemometric analysis (PCA, HCA and MDS) helped to identify volatiles, which could be used as biomarker in discriminating the AP‐P and AP‐NP isolates. VC pattern of rhizobacteria could be used as volatile markers to distinguish between AP‐P and AP‐NP rhizobacterial isolates. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
84.
Alka V. Deshmukh S.M. Yusuf N.P. Lalla 《Journal of magnetism and magnetic materials》2010,322(5):536-1217
Present study reports the detailed structural and magnetic, as well as chemical analysis of polycrystalline Zn1−xMnxO (where x=0, 0.005, 0.01, 0.03, 0.05 and 0.1) samples synthesized by the high-temperature solid state reaction route. X-ray diffraction studies reveal the presence of secondary phase for higher Mn-doping concentrations (x≥0.03). Secondary phase formation having spinel structure is confirmed and reported as an evidence for the first time using transmission electron microscopy study. Chemical investigations using X-ray photoelectron spectroscopy showed the presence of Mn in two valence states. From the observed results we are of the opinion that Zn2+ ions, mainly present at or near grain boundaries, diffuse into manganese oxide to form a stable spinel phase ZnxMn3−xO4 at or near the grain boundaries of ZnO/Zn1−xMnxO. Magnetization measurements did not show any magnetic transition down to 5 K. 相似文献
85.
In this paper we show that for a compact minimal hypersurface M of constant scalar curvature in the unit sphere S6 with the shape operator A satisfying ‖A‖2>5, there exists an eigenvalue λ>10 of the Laplace operator of the hypersurface M such that ‖A‖2=λ−5. This gives the next discrete value of ‖A‖2 greater than 0 and 5. 相似文献
86.
A novel method, based on the molecular tailoring approach for estimating intramolecular hydrogen bond energies, is proposed. Here, as a case study, the O-H...O bond energy is directly estimated by addition/subtraction of the single point individual fragment energies. This method is tested on polyhydroxy molecules at MP2 and B3LYP levels of theory. It is seen to be able to distinguish between weak ( approximately 1 kcal mol(-1)) and moderately strong ( approximately 5 kcal mol(-1)) hydrogen bonds in polyhydroxy molecules. 相似文献
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89.
Asymmetric synthesis of β-lactams by the [2+2] cycloaddition of ketenes with chiral imines derived from d-(+)-glucose was carried out; predominantly cis-β-lactams were formed with very high diastereoselectivity. The stereochemistry at C-3 and C-4 was established as 3S and 4R from the known absolute configuration of the sugar moiety. 相似文献
90.
Diastereoselective synthesis of spiro-β-lactams via [2+2] cycloaddition reaction of imines and chiral ketenes is described. The chiral ketene was prepared from commercially available, inexpensive d-glucose. Although, theoretically four diastereomers are possible, the reaction yielded only two diastereomers stereoselectively in good to moderate yields. The stereochemical outcome of the reaction was in accordance with the torquoelectronic model. 相似文献