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Title

ELECTROSYNTHESIS OF HEPARIN DOPED POLYPYRROLE AND ELECTROCHROMIC CHARACTERIZATION

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Abstract

 AN ELECTROCHROMIC MATERIAL IS THE ONE THAT CHANGES COLOR IN A PERSISTENT BUT REVERSIBLE MANNER BY AN ELECTROCHEMICAL REACTION AND THE PHENOMENON IS CALLED ELECTROCHROMISM. CONDUCTING POLYMERS (CPS) ARE FINDING INCREASING USE IN ELECTROCHROMIC APPLICATIONS BECAUSE OF THEIR CATHODIC, ANODIC AND MULTICOLOR CONTROL, EASE IN PROCESSABILITY, FLEXIBILITY, RAPID REDOX SWITCHING, HIGH OPTICAL CONTRAST, AND LONG-TERM STABILITY [1]. THE PHYSICAL MATERIAL PROPERTIES SUCH AS COLOR, CONDUCTIVITY, AND SURFACE ENERGY CAN BE CONTROLLED BY ELECTROCHEMICAL DOPING IN A CP. BY DOPING A CP, NEW ENERGY LEVELS ARE CREATED WITHIN THE BAND GAP DUE TO GENERATION OF POLARONS AND BIPOLARONS IN THE POLYMER BULK [2]. THE ELECTROCHROMIC PROPERTIES OF CPS HAVE BECAME OF GREAT IMPORTANCE IN MODERN REVERSIBLE ELECTRO-SWITCHING OPTICAL DESIGN OF POLYMER BASED OPTICAL SENSORS AND DEVICES. IN THIS PAPER, WE REPORT ON THE ELECTROCHEMICAL PREPARATION OF THE CONDUCTING POLYPYRROLE (PPY) SYNTHESIZED WITH ENTRAPPED HEPARIN (HEP) ANIONS. HEPARIN, A WIDELY USED ANTICOAGULANT, IS A HIGHLY SULFATED LINEAR NATURAL POLYSACCHARIDE [3]. THE ELECTROCHROMIC PROPERTIES OF POLYPYRROLE FILM ARE DIFFICULT TO EXPLOIT DUE TO THE DISSATISFACTORY STABILITY. WE HAVE CHOSEN HEP AS THE DOPING ANION SINCE ITS POLYANIONIC NATURE PREDICTS THAT IT WOULD INCREASE THE STABILITY OF PPY FILM. THE HEP-DOPED PPY WAS ELECTROCHEMICALLY SYNTHESIZED ON A FLUORINE DOPED TIN OXIDE FTO/GLASS ELECTRODE IN AQUEOUS SOLUTION. THE RESULTANT POLYMER WAS CHARACTERIZED VIA ELECTROCHEMICAL AND SPECTROELECTROCHEMICAL METHODS. THE SPECTROELECTROCHEMICAL ANALYSIS REVEALED THE PPY-HEP HAS DISTINCT ELECTROCHROMIC PROPERTIES WITH RESPECT TO THE PPY. POLYANIONDOPED POLYMER EXHIBITED A SWITCHING TIME OF LESS THAN 1.5 S AND THE MAXIMUM TRANSMITTANCE CONTRAST (DT%) IS 48% AT 800 NM. IN ADDITION PRESENCE OF HEP CAUSES DRASTIC ENHANCEMENT OF ELECTRO-OPTICAL STABILITY OF PPY. THE INTRODUCTION OF HEP POLYANION CAN LEAD TO ENHANCE THE FORMATION OF AN ORDERED PPY-BASED FILM WHICH CAN BE REASON FOR IMPROVEMENT OF STABILITY.

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