EEEEEEEEEEEE OF BLOCK COPOLYMERS Thermoplastic Elastomers, Block Copolymers, Styrene-Butadiene-Styrene

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  • AD-AG6 4i RENSSELAER POLYTECHNIC INST TROY N Y F/6 11/9

    MELT RHEOLOGY OF BLOCK COPOLYMERS IN RELATION TO MELT STRUCTURE--ETC(U) JUN 80 C I CHUNG DAA629-76-B-0334

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    * ELT kjEOLOGY OF -LOCK -OPOLYMERS IN RELATIONJ TO LT 1'Ti3CTUREI

    (CIC-ARo-8o-l) "/~C V J~ / 00 Final Report

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    U. S. AR'Y RESEARH OFFICE Grant No. DAAG29-76-G-0334; 78-G-0178

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    RENSSELAER POLYTECHNIC INSTITUTE Troy, New York 12181 D ISELECTE1

    AUG 4 198011

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    REPORT DOCUMENTATION PAGE MORE COMPLETING FORM 1. 1111ORT "Ume[N Gv? AccessIion NO. 3. ACCIP11E I'S CATALOQG NUM4119f

    CIC-ARO-80- 17 FI. AC 3. NECIPIEf -. TIrLetl (4040 S"0980) S. Typel Of Il9PORT" a P90100 COVERI[C MELT RHEOLOGY OF BLOCK COPOLYNERS IN RELATION Final Report

    TOSep. 24, 1976-arch 23, 19 4. PeRFORMING ORG. QEPCRT "UmeR

    7. ATWOR(e) S. CONTRACT O GRANT MUMOIR(S)

    C.I. Chung DAAG29-76-G-03$4'-' 78-G-0178

    9. .IwvrORMINO ORGANIZATION NAMC ANO ACODNESS W@. PROGRAM ECLIMENt PROJCT. TASK AREA A iORIC UNiT NUMS RS

    Rensselaer Polytechnic Institute/ Troy, New York 12181

    ti. CONTRpOLiN OPPica NAME AND AGGRIESS 12. REPORT OAT'U. S. AzW Research Office June 23, 1980 Post Office 3ox 12211 13.usE= OA Research Triangle Park, NC 27709 33

    14. MONITORING AGNCY NAMel AOORE(u1 di .eoll lm C609008:1004 01fi4e) I5. SECURITY CLASS. (el thie mpgs )

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    Approved for public release; distribution unlimited.

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    84. SuPP.EMENTARY MoOTES The view, opinions, and/or findings contained in this report are those of the author(s) and should not be construed as an official Department of the Army position, policy, or decision, unless so designated by other documentation.

    IS. KeY WOR S (Cr'.ifa a n elee odI nogoemp W e auwterp or coc mOsee ) Thermoplastic Elastomers, Block Copolymers, Styrene-Butadiene-Styrene Block Copolymer, Melt Rheology, Melt Structure, Morphology, Phase Separation, Phase Transition, Rheological Transition

    JIG. A1rW*9j r(Omm anr- w ShIP N~ rmE nd 1~0uF o black. mnoin) It is well known that block copolymers composed of incompatible polymers

    have multiphase structure, each component polymer being separated into its own phase, and their multiphase structure leads to unusual physical properties In particular, block copolymers composed of a soft polymer as the major com- ponent and a hard polymer as the minor component can have elastomeric pro- perties since the hard polymer blocks from different molecules segregate into hard domains dispersed in the soft matrix of the soft polymer blocks and

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    1Wthe hard domains serve as crosslinking and reinforcement. Some block copolymers of this nature are now successfully used as thermoplastic elasto-

    * mers.

    Block copolymers also exhibit unusual melt rheological properties, notably very high viscosity and elasticity in comparison to the component

    homopolymers of equal molecular weight. The unusual melt rheological properties have been attributed to the remnants of the multiphase structure which persist far above the glass transition or melting points of the com- ponent polymers.

    We found in this project that an experimental styrene-butadiene-styrene

    block copolymer upon heating exhibited a relatively sharp melt theological

    transition at a very high temperature from unusually high viscoelastic be- havior to the normal behavior expected of homopolymers. We also found using transmission electron microscopy, that the SBS sample underwent a morphological transition from multiphase structure to single-phase structure at a temperature corresponding to the melt rheological transition. Our findings clearly show that block copolymers can retain their multiphase structures to very high temperatures and their unusual melt rheological behavior comes from the multiphase structure in the melt.

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  • Foreword

    Block copolymer technology offers an opportunity to obtain unique poly-

    meric materials of exceptional properties ranging from high impact rigid

    polymers to high modulus elastomers through controlled synthesis and process-

    ing. The unique characteristics of block copolymers come from their multiphase

    structure which strongly depends on the chemical make-up and processing history.

    This project has made a step forward in understanding the development of multi-

    phase structure in block copolymers and the relationship between the Theological

    property and the structure in the molten state. The support of this project

    by the Army Research Office is sincerely appreciated.

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  • TABLE OF CONTENTS

    Foreword...................................................... i

    Introduction..................................................... 1

    Melt Rheology of Bicok Copolymers - Literature Review ...............3

    Theory of Phase Separation in Block Copolymers - A Brief Review ......8

    Experimental .................................................... 10

    Results and Discussion........................................... 10

    Test of Theories ................................................ 12

    Conclusion...................................................... 13

    References......................................................1IS

    Figures......................................................... vi

    List of Theses and Publications .................................. 27

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    v !

  • LIST OF FIGURES

    Figure 1. Schematic Representation of Five Possible Microdomain Structures of Block Copolymers

    Figure 2. Dynamic Viscosity as a Function of Angular Frequency.

    Figure 3. Dynamic Modulus as a Function of Angular Frequency.

    Figure 4. Reduced Dynamic Viscosity as a Function of Reduced Frequency.

    Figure S. Reduced Dynamic Modulus as a Function of Reduced Frequency.

    Figure 6. Electron Micrographs of the SBS Sample Annealed at 1200C.

    Figure 7. Electron Micrograph of the SBS Sample Quenched from 1250C.

    Figure 8. Electron ficrograph of the SBS Sample Quenched from 1700C.

    Figure 9. Electron Microggaph of SBS Sample Quenched from 190 0C and

    Annealed at 125 C.

    Figure 10. Dependence of the Predicted Phase Transition Temperatures on Solubility Parameter Difference for 7S-43B-7S Sample.

    Figure 11. Dependence of the Predicted Phase Transition Temperature on Energy Parameters for 7S-43B-7S Sample.

    vi

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  • 1.

    INTRODUCTION

    Block copolymers composed of imcompatible blocks have multiphase

    structure, each component being separated into its own phase. For

    example, the polystyrene blocks and the polybutadiene blocks in styrene-

    butadiene-styrene (SBS) block copolymers separate into their own phases.

    If polystyrene is the minor component of a SBS block copolymer, the poly-

    styrene phase becomes hard domains imbedded in soft matrix of the poly-

    butadiene phase. The hard polystyrene domains composed of polystyrene

    chain ends from different molecules act as physical crosslinks conferring

    to the SBS block copolymer elastomeric properties. Some SBS block co-

    polymers and other block copolymers of the same nature are now commercially

    used as thermoplastic elastomers.

    Because of the theoretical interest in the multiphase morphology of

    block copolymers as well as the industrial importance in block copolymers

    as thermoplastic elastomer, the research efforts on block copolymers have

    been quite extensive in the recent years and one can make a long list of

    * the articles published on block copolymers. However, the proceedings 4 -8

    j Iof the five symposia on block copolymers and multi-component polymers spon- sored by the American Chemical Society in 1967, 1969, 1970, 1974 and 1978

    will provide sufficient references for the purpose of this report. Estes,

    Cooper and Tobolsky9 published a review paper on block copolymers and re-

    lated heterophase elastomers. The Army Materials and Mechanics Research

    Center sponsored a symposium on block and graft copolymers in 1972.10

    Most recently, in late August 1979, Midland Macromolecular Institute held

    an International Symposium on Block Copolymers.

  • 2.

    The two-phase structure in block copolymers has been clearly demon-

    strated by electron microscopy4A'D 'SA-C,6A-D l' ,l2, small angle x-ray

    SD,6E 4C,SE-H,13 scattering5 '6 , thermal analysis '- , small angle lig