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61.
Sanders DP Fukushima K Coady DJ Nelson A Fujiwara M Yasumoto M Hedrick JL 《Journal of the American Chemical Society》2010,132(42):14724-14726
An improved two-step synthetic route to functionalized cyclic carbonate monomers that features a novel cyclic carbonate intermediate with an active pentafluorophenyl ester group (MTC-OPhF(5)) has been developed. The versatile pentafluorophenyl ester intermediate can be synthesized on the gram to kilogram scale in one high-yielding step and is easy to store and handle on the benchtop. The active pentafluorophenyl ester of MTC-OPhF(5) is amenable to further substitution with suitable nucleophiles such as alcohols and amines to generate functionalized cyclic carbonates in high yields. The substitution reaction is tolerant of a wide variety of functionalities, including various hydrophobic and hydrophilic groups, reactive functionalities (via thiol-ene click chemistry or alkyl halides), and protected acids, alcohols, thiols, and amines. In view of the ever-increasing need for biodegradable and biocompatible polymers, this new methodology provides a simple and versatile platform for the synthesis of new and innovative materials. 相似文献
62.
Dove AP Li H Pratt RC Lohmeijer BG Culkin DA Waymouth RM Hedrick JL 《Chemical communications (Cambridge, England)》2006,(27):2881-2883
New sterically encumbered N-heterocyclic carbene catalysts were synthesized and used to polymerize rac-lactide to give highly isotactic polylactide or meso-lactide to give heterotactic polylactide. 相似文献
63.
Malkoch M Vestberg R Gupta N Mespouille L Dubois P Mason AF Hedrick JL Liao Q Frank CW Kingsbury K Hawker CJ 《Chemical communications (Cambridge, England)》2006,(26):2774-2776
New PEG-based hydrogel materials have been synthesized by Click chemistry and shown to result in well-defined networks having significantly improved mechanical properties; the selectivity of the azide/acetylene coupling reaction also allows for the incorporation of various additives and functional groups leading to chemical tailoring of the hydrogels. 相似文献
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Robert Jr
me David Mecerreyes Dong Tian Philippe Dubois C. J. Hawker M. Trollsas J. L. Hedrick 《Macromolecular Symposia》1998,132(1):385-403
Combination of the living ring-opening polymerization (ROP) of ε-CL and lactides with the “controlled” free radical polymerization of styrene and methacrylic monomers is a versatile strategy for the synthesis of well-defined block and graft copolymers. In this respect, the dual “living” polymerization strategy in which two different functional groups on a single molecule used to initiate the two controlled mechanisms is particularly efficient. Combination of ROP and step-growth polymerization is another versatile methodology for the preparation of a large variety of new materials, e.g. polyimide nanofoams, polyester/silica hybrid materials and star and branched polyesters by dendritic initiation. 相似文献
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MP Janawadkar R Baskaran R Nagendran K Gireesan N Harishkumar Rita Saha L S Vaidhyanathan J Jayapandian Y Hariharan TS Radhakrishnan 《Pramana》2002,58(5-6):1159-1164
A program has been developed and initiated at the Indira Gandhi Centre for Atomic Research (IGCAR) for the utilization of
SQUID sensors in various application areas. DC SQUID sensors based on Nb-AlO
x
-Nb Josephson junctions have been designed and developed inhouse along with associated flux-locked loop (FLL) electronics.
A compact low field SQUID magnetometer insertible in a liquid helium storage dewar has also been developed inhouse and is
in use. Efforts to build a high field SQUID magnetometer, SQUID-DAC system, are in progress. A planar gradiometric DC SQUID
sensor for non-destructive evaluation (NDE) application to be used in relatively unshielded environment has been designed
and developed. An easily portable NDE cryostat with a small lift-off distance, to be used in external locations has been designed
and tested. The magnetic field produced by a given two-dimensional current density distribution is inverted using the Fourier
transform technique. 相似文献
70.
Coady DJ Fukushima K Horn HW Rice JE Hedrick JL 《Chemical communications (Cambridge, England)》2011,47(11):3105-3107
Herein, we report the use of acid/base complexes for the ring opening polymerization of (L)-lactide. The salt formed from an equimolar reaction of benzoic acid and DBU produced a catalyst capable of controlled polymerizations allowing for targeted molecular weights and narrow polydispersities. The use of computational analysis suggests a bifunctional catalytic mechanism wherein both the monomer and propagating hydroxyl group are activated toward polymerization. 相似文献