DIELECTRIC AND PYROELECTRIC PROPERTIES OF POLY[2,3-BIS(TRIFLUOROMETHYL)NORBORNADIENE]
DIELECTRIC AND PYROELECTRIC PROPERTIES OF POLY[2,3-BIS(TRIFLUOROMETHYL)NORBORNADIENE]
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DOI：
10.1016/0032-3861(95)91309-u
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发表时间：
1995-01-01
期刊：
影响因子：
4.6
通讯作者：
MARSHALL, EL
中科院分区：
文献类型：
--
作者：
DAVIES, GR;HUBBARD, HVS;MARSHALL, EL
以W、Mo或Ru为引发剂，通过开环歧化聚合合成了含氟聚合物聚[2，3-双(三氟甲基)降冰片二烯](Poly(BTFMND))，得到了反式乙烯含量可控的聚(BTFMND)。对C-13核磁共振精细结构的分析表明，高反式(>；98%)聚合物是92%的TARIT，高顺式(>；98%)聚合物是75%TARIT，但这些方法不能确定材料主要是等规的还是间规的。进行了介电和热刺激电流测量，得到了介电常数epsilon(R)与反式含量密切相关，范围从98%反式材料的40以上到54%反式聚合物的15到98%顺式聚合物的6。高反式材料的T-g以上介电常数显著高于54%反式聚合物，98%顺式聚合物的介电常数显著降低，这表明高顺式和高反式材料都具有间规结构。98%反式聚(BTFMND)的总极化在约20mCm(-2)处饱和，在200 mVm(-1)的极化场上热释电系数接近6mCm(-2K-1)。这些有用的高值与常温下玻璃态的低介电损耗相结合，表明了一种潜在的用作热释电换能器的优良材料，其优值系数可与聚偏氟乙烯相当或更好。
The fluoropolymer poly[2,3-bis(trifluoromethyl)norbornadiene] (poly(BTFMND)) has been synthesized via ring-opening metathesis polymerization, using initiators based on W, Mo or Ru compounds or via variations of the Schrock-type initiator Mo(CHR)(N-2,6-C6H3-i-Pr-2)(OR')(2) (R=CMe(3), CMe(2)Ph; R'=CMe(3), CMe(CF3)(2)), giving poly(BTFMND) with controllable proportions of trans-vinylene units. Analysis of the C-13 nuclear magnetic resonance fine structure establishes that the high-trans (>98%) polymer is 92% tactic and the high-cis (>98%) polymer is 75% tactic, but these methods cannot determine whether the material is predominantly isotactic or syndiotactic. Dielectric and thermally stimulated current measurements have been performed and give relaxed permittivities epsilon(R) strongly dependent on trans content, ranging from above 40 for the 98% trans material through 15 for the 54% trans polymer to 6 for 98% cis polymer. The significantly higher permittivity above T-g for the high-trans material than for the 54% trans polymer and the significantly reduced value for the 98% cis polymer suggest that both the high-cis and high-trans materials have syndiotactic structures. The total polarization for free films of 98% trans poly(BTFMND) saturates at about 20 mC m(-2), with a pyroelectric coefficient approaching 6 mu C m(-2) K-1 above poling fields of 200 MV m(-1). These usefully high values combined with low dielectric loss in its glassy state at ambient temperatures indicate an excellent material for potential use as a pyroelectric transducer, with a figure of merit comparable with or better than that of poly(vinylidene fluoride).