85  US 7,511,179 B2  86  The copolymer was one comprising TFE/cyclooctene in a  percent by mole ratio of 52/48 according to an elementary  was used instead of cyclopentene.  Reaction was carried out in the same manner as in Example  1 except that 3.5 g of 2,3-dihydrofuran:  After releasing the un-reacted monomer, the polymeriza› tion solution was removed, followed by re-precipitation with  methanol to separate a copolymer. Until a constant weight  was reached, vacuum drying was continued and 2.7 g of a  copolymer was obtained. As a result of $^{1 }$H-NMR analysis, the  copolymer was one represented by the following formula.  The copolymer was one comprising TFE/cyclopentene in a  percent by mole ratio of 50/50 according to an elementary  analysis. According to GPC analysis, a number average  molecular weight of the copolymer was 5,700.  40 ml ofHCFC-141 band 0.4 g of bis( 4-tert-butylcyclohexyl)  peroxydicarbonate (TCP), and the inside of a system was  sufficiently replaced with nitrogen gas while cooling with dry  ice/methanol solution. Then 10.0 g of tetrafluoroethylene  (TFE) was introduced through a valve, followed by shaking  for reaction at 40°  C. for 18 hours. With the advance of the  reaction, a gauge pressure was decreased from 0.88 MPaG  (9.0 kgf/cm $^{2}$G) before the reaction to 0.84 MPaG (8.6 kgf/  cm $^{2}$G).  Example 2  Example 3  Example 1  A 100 ml autoclave was charged with 3.4 g of cyclopen› tene:  After releasing the un-reacted monomer, a polymer was  separated in the same manner as in Example 1 and 2.1 g of a  copolymer was obtained. As a result of $^{1}$H-NMR and $^{19}$F› NMR analyses, the copolymer was one represented by the  following formula.  With the advance of the reaction, a gauge pressure was  decreased from 0.78 MPaG (8.0 kgf/cm $^{2}$G) before the reac› tion to 0.75 MPaG (7.7 kgf/cm $^{2}$G).  The copolymer was one comprising TFE/2,3-dihydrofuran  in a percent by mole ratio of 50/50 according to an elementary  analysis. According to GPC analysis, a number average  molecular weight of the copolymer was 17,000.  A 100 ml autoclave was charged with 2.8 g of cyclooctene:  40 ml ofHCFC-141 band 0.3 g of bis( 4-tert-butylcyclohexyl)  peroxydicarbonate (TCP), and the inside of a system was  sufficiently replaced with nitrogen gas while cooling with dry  ice/methanol solution. Then 10.0 g of tetrafluoroethylene  (TFE) was introduced through a valve, followed by shaking  for reaction at 40°  C. for 18 hours. With the advance of the  reaction, a gauge pressure was decreased from 0.78 MPaG  (8.0 kgf/cm $^{2}$G) before the reaction to 0.75 MPaG (7.7 kgf/  cm $^{2}$G).  After releasing the un-reacted monomer, the polymeriza- tion solution was removed, followed by re-precipitation with  hexane to separate a copolymer. Until a constant weight was  reached, vacuum drying was continued and 1.5 g of a copoly› mer was obtained. As a result of $^{1}$H-NMR and $^{19}$F-NMR  analyses, the copolymer was one represented by the follow- ing formula.  -(CF2CF2v  Synthesis of Copolymer Comprising  2,3-dihydrofuran and Tetrafluoroethylene  Synthesis of Copolymer Comprising Cyclooctene  and Tetrafluoroethylene  Synthesis of Copolymer Comprising Cyclopentene  and Tetrafluoroethylene  (2) IR analysis: Measuring is carried out at room temperature  with a Fourier-transform infrared spectrophotometer  1760X available from Perkin Elmer Co., Ltd.  (3) GPC: A number average molecular weight is calculated  from data measured by gel permeation chromatography  (GPC) by using GPC HLC-8020 available from Toso  Kabushiki Kaisha and colunms available from Shodex Co.,  Ltd. (one GPC KF-801, one GPC KF-802 and two GPC  KF-806M were connected in series) and flowing tetrahy› drofuran (THF) as a solvent at a flowing rate of 1  ml/minute. 