氏名　Makbul Anawari
学位の種類　博士（工学）
学位記番号　博甲第366号
学位授与の日付　平成18年03月24日
学位論文題目　PTC Thermistor Materials Based on Conducting Poly（3-hexylthiophene）導電性ポリ（3-ヘキシルチオフェン）をベースとしたPTCサーミスター材料）
論文審査委員
　主査　教授　宮内　信之助
　副査　助教授　丸山　一典
　副査　助教授　下村　雅人
　副査　助教授　木村　悟隆
　副査　長岡工業高等専門学校教授　反町　嘉夫

• 論文目次
• 論文要旨
• 論文審査の結果の要旨

［平成17（2005）年度博士論文題名一覧］ ［博士論文題名一覧］に戻る．

Contents

1. General introduction

　1.1　Preface　p.1
　1.2　Conducting polymer composite materials （CPCM）　p.2
　1.3　PTC effect of CPCM　p.6
　1.4　NTC effect of CPCM　p.11
　1.5　Development ofPTC thermistors in the latest decade　p.12
　1.6　PTC effect of pofy （3-hexylthiophene） and its composites　p.15
　1.7　Constitution ofthisdissertation　p.18
　1.8　References　p.20

2. Conductivity-Temperature Characteristics of Polyiso-thianaphthene and Poly（3-hexylthiophene） Blends

　2.1　Introduction　p.24
　2.2　Experimental　p.26
　2.2.1 Materials　p.26
　2.2.2 Synthesis of P3HT　p.26
　2.2.3 Synthesis of PITN　p.27
　2.2.4 Preparation ofPITN/P3HT Blends　p.27
　2.2.5 Conductivity measurement　p.28
　2.2.6 Scanning Electron Microscopy （SEM）　p.28
　2.3　Results and Discussion　p.29
　2.3.1 Synthesis and conductivity of PITN　p.29
　2.3.2 Conductivity-temperature behavior of PITN/P3HT Blends　p.32
　2.3.3 Morphological study of PITN-P3HT Blends　p.34
　2.3.4 Results of the heating recycle　p.37
　2.4　Conclusion　p.39
　2.5　References　p.41

3. Influence of Irradiation on the Conductivity-Temperature Characteristics of Poly（3-hexylthiophene） and Its blend with Poly（isothianaphthene）

　3.1　Introduction　p.43
　3.2　Experimental　p.44
　3.2.1 Materials and preparation　p.44
　3.2.2 Irradiation　p.44
　3.2.3 Gel content measurement　p.45
　3.2.4 Characterization　p.45
　3.3　Results and Discussion　p.45
　3.3.1 Crystalline character of P3HT　p.45
　3.3.2 Relationship between gel content and irradiation doses p.47
　3.3.3 X-ray analysis of irradiated P3HT samples　p.48
　3.3.4 DSC results of irradiated P3HT samples　p.50
　3.3.5 Dynamic mechanical properties　p.50
　3.3.6 Conductivity-temperature behavior of irradiated P3HT　p.53
　3.3.7 Conductivity-temperature behavior of the irradiated blend　p.54
　3.4　Conclusion　p.56
　3.5　References　p.57

4. Preparation of Poly（3-hexylthiopene）-Grafted Indium Tin Oxide / Poly（3-hexylthiopene） Composite and Its Conductivity-Temperature Characteristics

　4.1　Introduction　p.59
　4.2　Experimental　p.60
　4.2.1 Materials　p.60
　4.2.2 Preparation of P3HT-grafted ITO particles　p.61
　4.2.2.1 Silanization　p.61
　4.2.2.2 Condensation　p.62
　4.2.2.3 Grafting　p.62
　4.2.3 Preparation of P3HT-grafted ITO / P3HT composites　p.62
　4.2.4 Preparation of ungrafted ITO / P3HT composites　p.63
　4.2.5 Sample-preparation and measurement　p.63
　4.3　Results and Discussion　p.63
　4.3.1 Grafting reaction of P3HT onto ITO surface　p.63
　4.3.2 Grafted amount of P3HT on the surface of ITO particles　p.65
　4.3.3 Temperature dependence of conductivity of P3HT-grafted ITO particles　p.67
　4.3.4 Conductivity-temperature characteristic of P3HT-grafted ITO / P3HT composites　p.68
　4.3.5 Comparison of the grafted composite with the ungrafted composites　p.71
　4.4　Conclusion　p.74
　4.5　References　p.75

5. Anisotropic Conductivity-temperature characteristic of Solution-Casting P3HT Films with High Orientation

　5.1　Introduction　p.77
　5.2　Experimental　p.78
　5.2.1 Preparation ofP3HTs　p.78
　5.2.2 Measurement of conductivity　p.79
　5.3　Results and Discussions　p.79
　5.3.1 Structure anisotropy　p.79
　5.3.2 Anisotropioconductivity　p.82
　5.3.3 Anisotropic conductivity-temperature characteristics　p.82
　5.3.4 Influence of thermal recycles on conductivities in two directions　p.86
　5.4　Conclusion　p.92
　5.5　References　p.92

6. General conclusion　p.95

Publication List　p.98

Acknowledgement　p.99

　The electrical conductivity of conducting poly（3-hexylthiophene） （P3HT） shows a switching characteristic with the positive temperature coefficient （PTC） effect around its melting point, due to a reversible change of effective conjugated length caused by the trans-gauche conformation transition of hexyl side chains with heating recycles. The PTC mechanism of P3HT is greatly different from the PTC phenomenon observed in conventional PTC materials composed by conducting polymer composites. In order to explore the possibility of conducting P3HT applied as PTC thermistors, the conductivity-temperature characteristics of intrinsic P3HT and its composites filled with various filler particles are extensively studied in this work.

The conductivity-temperature characteristics of blends consisting of polyisothan aphthene （PITN） particles and soluble P3HT were investigated. Conducting PITN was synthesized by direct conversion of 1,3-dihydroisothianaphthene （DHITN） monomer using N-chloro- succinimide （NCS） as an oxidation / dehydrogenation reagent. The high conductivity and thermal stability of doped and dedoped PITN particles were confirmed. Microscopic investigation by SEM showed that the as- prepared PITN exhibited diversified shapes and sizes, with large rectangular particles having an average size of 2 ~ 5 μm and fine round particles ranging from 0.1 to 0.3 μm. The PITN particles were blended with the chemically synthesized P3HT as a high conductivity component to improve the conductivity and simultaneously maintain the PTC effect of the original P3HT near its melting point. The conductivity-temperature characteristics of PITN-P3HT blends with various PITN contents showed that a blend having both a high conductivity （nearly 3~4 orders higher than that of the original P3HT） and a good PTC intensity could be obtained with a PITN contents of 20 ~ 25%. The different conductivity- temperature behavior of P3HT blends filled with PITN as compared to other conducting particles, e.g. carbon black, was explained by its unique dispersion structure due to a relatively higher adhesive interaction of PITN particles with the P3HT matrix during the precipitation process. The results from heating recycles revealed that the PTC effect of PITN-P3HT blends was not just related to the conductivity decrease of the P3HT matrix, arising from the conformational change of the conjugated backbone during the melting, but also to the dilution effect of the conducting percolation network due to the mobility of PITN particles induced by the viscosity decrease of the P3HT matrix.

In order to improve the electrical stability and PTC reproducibility of the above PITN-P3HT blends with thermal recycles, the influences of irradiation on the conductivity- temperature characteristics of P3HT and PITN/P3HT blends were investigated. Results from gel content, X-ray, DSC, and DVE showed that the irradiation-induced crosslinking in P3HT mainly occurred between the hexyl side chains in the amorphous regions. The PTC effect of intrinsic P3HT was remained but with reduced intensity, since the change of conjugated length caused by the thermal disturbance of side chains was restrained in a certain degree by the side chain crosslinking. Although the PTC mechanism of PITN/P3HT blends was different from conventional PTC materials, the radiation treatment was proved same effective to improve the electrical stability and PTC reproducibility of PITN/P3HT blends.

The conductivity-temperature characteristics of a P3HT composite filled with P3HT- grafted indium tin oxide （ITO） particles were investigated. The ITO particles were, first, treated with a silane coupling reagent of 3-aminopropyltr iethoxysilane （APS）, and then thiophene rings were introduced through a condensation reaction between the ending amino group of APS and the carboxylic group of thiophene-3-acetic acid （T3A）. The composites were prepared by the polymerization filling of the 3-hexylthiophene （3HT） monomer with the thiophene- ring-introduced ITO particles. Elemental analysis, FT-IR and X-ray photoelectron spectroscopy were used to confirm the grafting reaction on the ITO surface. The grafted amount of P3HT on the ITO surface was influenced by polymerization conditions; i.e. the longer the reaction time was or the higher the feeding ratio of 3HT monomer to ITO particles was, the more P3HT was grafted. The influence of the grafted amount on the electrical properties of ITO particles was attributed to the wrapping effect formed by the grafted P3HT on the surface of the ITO particles. The conductivity change of the P3HT-grafted ITO / P3HT composites was proved to be subject to the change in the average gap width of ITO interparticles, which was determined by the filling ratio of P3HT to ITO in the polymerization and the volume expansion effect of a P3HT thin film between neighboring ITO particles during the heating process. In comparison with the ungrafted-ITO / P3HT composites, the grafting treatment enhanced the interaction between the particles and polymer matrix, and this was helpful for obtaining a more homogeneous dispersion structure for the composites and thus afforded a higher PTC intensity and better reproducibility.

Aiming to develop a thin film PTC device based on the soluble P3HT, high molecular weight （Mw） P3HT films with various regioregularities were prepared by solution casting from chloroform. The structure anisotropy and temperature dependence of conductivities measured in the directions parallel （σ//） and perpendicular （σ⊥） to the film surface were investigated. For highly- orientated P3HT films the temperature dependence of σ⊥ was shown as a thermal activated increase, due to the amorphous character of charge hopping, whereas the σ// decreased greatly after 50 ℃, owning to a decrease of in-plane π-stacking caused by the melting of side chain crystallization and the consequently enhanced disturbance with increasing temperature. Different charge transport mechanisms were proposed to explain the above anisotropic conductivity-temperature characteristics observed in two directions. The high conductivity in the parallel direction was deteriorated significantly after thermal recycles, which was attributed to a reduction in the orientation degree of crystallites in the bulk film, rather than a change of effective conjugated length of polymer backbone. A reversible PTC effect was observed in P3HT film in the perpendicular direction with high Mw and medium regioregularity, which indicated that the high Mw was probably more important than high regioregularity to design the thin film PTC devices based on soluble P3HT films.

The present study demonstrated that the novel PTC effect of conducting P3HT, no matter shown by the intrinsic P3HT casting films or by the composites filled with various filler particles, could be greatly expected to apply as PTC thermistor materials.

　本論文は、「Conductivity-Temperature Characteristics of Polyisothianaphthene and Poly（3-hexylthiophene） Blends（導電性ポリ（3-ヘキシルチオフェン）をベースとしたPTCサーミスター材料）」と題し、以下のように6章から構成されている。

第一章「緒論」では、従来のPTCサーミスター材料および導電性P3HTのPTC原理について紹介し、本研究の目的を述べた。

第二章「Conductivity-Temperature Characteristics of Polyisothianaphthene and Poly（3-hexylthiophene） Blends（ポリ（イソチアナフテン）とポリ（3-ヘキシルチオフェン）のブレンドの導電－温度特性）」では、高い導電率および高い熱安定性を持つ導電性PITNを充填粒子としてP3HTマトリックスに導入し、このPITN/P3HTブレンドは従来のCBとITO粒子を充填したP3HTブレンドと異なるPTC特性を示した。PITN粒子はほかの粒子と比べてより高い粘性相互作用を示すため、P3HTマトリックス中で異なる分散状態になると考えた。また、熱サイクルの結果から、PITN/P3HTブレンドのPTC特性は高温の時P3HTマトリックスの粘性が低下するため、PITN粒子の移動に帰因する導電ネットワークの濃度の減少に関与すると考えた。

第三章「Influence of Irradiation on the Conductivity-Temperature Characteristics of Poly（3-hexylthiophene） and Its Blend with Poly（isothianaphthene）（放射線によるP3HTとPITN/P3HTブレンドの導電―温度特性の影響）」では、前章のPITN/P3HTブレンドのPTC強度および再現性を向上させるため、P3HTとブレンドに対して放射線処理を行った。放射線処理により架橋は主にP3HTの側鎖の間に発生することがわかった。また、放射線処理は高温下でのPITN粒子の移動を防ぐため、PITN/P3HTブレンドの電子安定性とPTC再現性が向上した。

第四章「Preparation of Poly（3-hexylthiopene）-Grafted Indium Tin Oxide / Poly（3-hexylthiopene） Composite and Its Conductivity-Temperature Characteristics（P3HTグラフトITO/P3HT複合体の作製および導電―温度特性）」では、表面にP3HTをグラフトしたITO粒子とP3HTの複合体を作製し、導電―温度特性を調べた。この複合体の導電率の変化は、重合反応による3HT/ITOの比率および昇温過程中のP3HTの熱膨張からITO粒子の平均間隔の変化と一致していると考えた。グラフト処理が導電粒子とポリマーマトリックスの間の相互作用を増加させるため、未処理の複合体と比べて、PTC特性と再現性が向上することがわかった。

第五章「Anisotropic Conductivity-Temperature Characteristic of Solution-Casting P3HT Films with High Orientation（高配向性を持つP3HT溶液キャスト膜の異方導電―温度特性）」では、薄膜PTCデバイスの応用を目的として、異なる構造規則性を持つ高分子量のP3HTキャスト膜を作製し、膜表面に対して平行と垂直方向の導電―温度特性を調べた。高配向性を持つP3HT膜は平行方向の方がより高い導電率を示した。また、垂直方向の導電率は温度上昇によって連続的に増加し、平行方向の導電率は50℃以降では低下することがわかった。この導電率の減少は、P3HT側鎖の結晶の融解に関係すると考えた。また、平行方向の高い導電率が熱サイクルにより低化したことは、P3HTの共役構造の変化ではなく、P3HT結晶体の配向性の低下であると考えた。

第六章「総括」では本研究で得られた成果を総括した。

本研究の結果は過電流保護素子などの基礎特性として重要で、工学上・工業上貢献するところが大きい。よって、審査の結果、博士（工学）の学位を授与できると認める。