Browsing by Author "Chu, PPJ"

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Conformational conversion and local packing of cyclic olefin copolymers
(2000-12-12)
Chu, PPJ
;
Cheng, MH
;
Huang, WJ
;
Chang, FC
;
應用化學系
Cyclic olefin copolymer (COC, poly(norbornene-co-ethylene)) catalyzed by ansa-ethylenebis-(indenyl)zirconium dichloride (Et[Ind](2)ZrCl2)/methylaluminoxane (MAO) gives rise to phenomenal increase of T-g upon annealing. Unaveraged solid-state C-13 NMR resonance of the CH carbons in the norbornene (53 and 49 ppm) evidenced the conformation conversion from T[X]T and G[M]G to more stable T[X]G conformers (where [X] = [T] or [G] represent the norbornene chain conformation). As the persistent length increases with the conversion, local packing of the rigid chain subsequently occurs. Synchrotron source X-ray diffraction provides clear evidence of the averaged interchain contraction from 12.0 to 8.5 Angstrom and a tighter distribution in the spacing after annealing. In the preannealed state, T-1p(H) relaxation time revealed both mobile (where conformer converts) and rigid components (where conformation is frozen), which coalesce into a further rigid component after extended annealing. The mechanisms governing the packing in amorphous COC are likely by the random chain diffusion and not from cooperative motion as described by the bundle-packing model.
Copolymerization of norbornene with ethylene: a high-resolution liquid NMR, DSC and solid state NMR study
(2000-03-01)
Huang, WJ
;
Chang, FC
;
Chu, PPJ
;
應用化學系
;
Department of Applied Chemistry
In this paper, we report the monomer reactivity on the copolymerization of norbornene and ethylene. The reactivity ratios for ethylene (M-1) and norbornene (M-2) are 18.5 and 0.035, respectively. Different copolymerization conditions can produce COC with different microstructures. A C-13 NMR shift assignment in pentad sequences in copolymers has been obtained. More isolated polynorbornene or a micro-block length can be obtained using a low Zr/Al catalyst/co-catalyst ratio and at a lower NB/ethylene feed ratio. The T-1p(C) decay curve shows two component decays in all resonance peaks. These two component decays come from different norbornene microstructures, while the block and alternative have similar T-1p(C) values.
Functionalization and chemical modification of cyclo olefin copolymers (COC)
(2000-07-01)
Huang, WJ
;
Chang, FC
;
Chu, PPJ
;
應用化學系
;
Department of Applied Chemistry
In this paper, we report two simple and effective bromination methods to brominate the cycle olefin copolymer (COC). A suitable metallic catalyst can accomplish functionalization and chromophorization of the brominated COG. A 2nd NLO dye, Disperse Orange 3(DO3) containing the -NH2 functional group, has been grafted onto either the norbornene unit or the PE segment of the COC backbone successfully, by the palladium catalyst, Pd-2(dba)(2)(Bis[dibenzylideneacetone] dipalladium). The observed low dye grafting content can be attributed to the higher hindrance of the norbornene ring. Based on UV results, the NLO-COC, having dye grafted onto the norbornene unit shows more red shift than that grafted onto the PE unit, probably due to greater shielding on the chromorphor. (C) 2000 Elsevier Science Ltd. All rights reserved.
Kinetics for the growth of rigid amorphous fraction in cyclic olefin copolymers (COC)
(2001-03-01)
Chu, PPJ
;
Huang, WJ
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Both linear William-Watts (WW) and non-linear Narayanaswamy-William-Watts (NWW) stretch relaxation satisfactorily described the time dependent rigid amorphous phase growth kinetic. The model is tested upon the completely amorphous cyclic olefin copolymers (COC, polynorbornene/polyethylene copolymer), where a large T-g variation is detected with annealing. Increase of the rigid amorphous fraction as reflected in the increase of T-g, is attributed to the growth of short range ordered phase due to the rigidity of the norbornene chain segment. The analysis shows the growth kinetic (represented by the retardation time, and the stretch exponent) that depends not only on the norbornene (NB) content but also on the NE microblock structure. The kinetics for the growth of the rigid amorphous domains follows a stretched exponential expression, similar to that given for polymer crystallization and physical aging. (C) 2000 Elsevier Science Ltd. All rights reserved.
Solid-state NMR study of cyclo-olefin copolymer (COC)
(2000-10-01)
Huang, WJ
;
Chang, FC
;
Chu, PPJ
;
應用化學系
;
Department of Applied Chemistry
In this article, we have applied solid-state C-13 NMR techniques, cross-polarization/magic-angle spinning (CP/MAS), and single-pulse C-13 NMR to characterize the NE conformation of the cyclo-olefin copolymer. The copolymers containing higher NE contents produce more NE blocks according to C-13 CP/MAS spectral analysis. In addition, NB-dyad-based conformations are able to induce peak splitting in the region of 49-52 ppm. (C) 2000 John Wiley & Sons, Inc.