Polymer and Soft Material Research (PSMR) Group

                                                 Research Work

 

The research in our group is focused on developing novel p-Conjugated Polymers for potential application in energy harvesting and storage devices as well as for application as sensors. One of the main underlying principle of the research work is to make use of molecular self-organization to build higher ordered polymer architectures which can find potential applications in the opto-electronic industry. Details of the research activities currently being pursued in the group are given below.

In the recent years our group has ventured into the exciting research of material development for 3D printing or Additive Manufacturing. Three dimensional printing (3DP), or additive manufacturing is a revolutionary or disruptive technology which is impacting wide areas of applications ranging from automotive industry to biomedical materials. The material requirement catering to the different AM technologies like material extrusion, material jetting, Vat photopolymerization, etc are in different forms – solid powder, liquid, paste or fiber. The wide scope for material development is both challenging and exciting. Glimpses of our foray into this exciting research area is given below.

 

p-Conjugated Polymers for Energy Harvesting and Storage Applications

Donor-acceptor pi conjugated polymers are emerging as interesting electrode materials for supercapacitor device applications. They offer the exciting possibility of charge storage in both positive and negative electrodes since they are both p and n dopable. The ambipolar charging enables higher operating voltage, which can afford higher specific energy and power densities. The donor-acceptor design can be either donor-alternate-acceptor or donor-random-acceptor. This architectural variation has the potential to modify the charge storage; yet surprisingly not much literature data is available exploiting this aspect. Research in our group explored the alternate and random geometries of donor-acceptor p-conjugated polymers based on naphthalene diimide (NDI) or perylene diimide (PDI) as the acceptor component and benzodithiophene (BDT) as the donor component and their application as composite electrode materials in Type III supercapacitor device. Results showed that the donor-acceptor alternate design involving P(PDI-alt-BDT) is an excellent supercapacitor electrode material with specific capacitance of 113 F g-1 with excellent stability up to 4000 cycles and almost 100% retention of the initial capacitance in single electrode setup in PC-LiClO4 organic electrolyte. Flexible supercapacitor device were also fabricated which showed areal capacitance of 35 mF cm-2 at a current density of 0.5 mA cm-2, which is promising for commercial application.

 §      Sharma, Sandeep; Soni, Roby; K. Sreekumar*; S. K. Asha* Rylene Diimide Based Alternate and Random Copolymers for Flexible Supercapacitor Electrode Materials with Exceptional Stability and High Power Density. J Phys Chem C, 2019123 (4), 2084–2093.

§      Sharma, Sandeep; Soni, Roby; K. Sreekumar*; S. K. Asha* Naphthalene Diimide Copolymers by Direct Arylation Polycondensation as Highly Stable Supercapacitor Electrode Materials. Macromolecules, 201851, 954–965.

 

Enantioselective Separation Using Chiral Amino Acid Functionalized Polyfluorene Coated on Mesoporous Anodic Aluminium Oxide (AAO) Membranes

Homochiral mesoporous anodic aluminium oxide membranes (AAO) were prepared by coating protected chiral D/L aspartic acid appended polyfluorene in the pores. These chiral AAO membranes successfully demonstrated enantioselective recognition and separation of a range of amino acids from their aqueous racemic mixture by simple filtration. Enantioselective separation was achieved by selective adsorption of one enantiomer from the aqueous racemic mixture into the chiral pores of the AAO membrane leaving the filtrate enriched with the other enantiomer. Extraction and quantification of the adsorbed amino acid (glutamic acid) demonstrated that 1 mg of homochiral polyfluorene could effectively extract about 3.5 mg of glutamic acid with 95 % enantiomeric excess in 24 h. This is one of the highest enantiomeric excess (ee %) and yields reported so far in literature for racemic mixture of glutamic acid. The pore size of the AAO membrane influenced the efficiency of separation with a reduction in pore size from 200 nm to 20 nm leading to reduced ee % (~ 95 % to ~ 28 %). These results raise the possibility for a facile method to carry out enantioselective separation.

 

§      Shrikant B. Nikam, Asha SK*. Enantioselective Separation Using Chiral Amino Acid Functionalized Polyfluorene Coated on Mesoporous Anodic Aluminum Oxide Membranes. Analytical Chemistry 2020, 92, 6850−6857.

 

Block Polymers Self Assembly

Research in this field is directed towards developing nanostructured polymeric or oligomeric assemblies based on the n type semiconducting system –Rylenebisimides.

A ditopic molecular probe bispentadecylphenol substituted perylenediimide (PBI-PDP) was used to examine the molecular level self-assembly of Polystyrene-b-Poly(4-vinyl pyridine) (PS-b-P4VP) in tetrahydrofuran (THF). A series of complexes were prepared between PS-b-P4VP copolymers with varying lengths of the 4-vinylpyridine chain and PBI-PDP. Light scattering and NMR spectroscopic studies reveal that the self-assembled structures of the solid complexes are not fully disrupted when the complexes are dissolved in THF. NMR experimental parameters measured for the small probe molecule provides detailed insights into the structure of the assemblies in solution as well as the interaction between the small molecule and the block copolymer. Such insights can have important implication in manipulating the nanostructure of block copolymer micelles to suit various application requirements. The dynamics and distribution of the PBI-PDP molecules within the assemblies in solution shows a dependence on the length of the P4VP block. Transmission electron microscopy was employed to study the evolution of morphologies in films prepared from the self-assembled structures in THF solutions.

 

§      Moumita Roy, Pattuparambil R. Rajamohanan, Sapna Ravindranathan,* and Asha S. K* Self-Assembly of Bispentadecylphenol Substituted Perylenediimide with PSbP4VP for StructureProperty Insight into the Core of Core−Shell Micelles. ACS Appl. Polym. Mater. 2020, 2, 805−816 DOI: 10.1021/acsapm.9b01099

 

Fluorescent Polystyrene Nanobeads for Visual Detection of Bilirubin in Human Blood Serum

Amphiphilic polystyrene having pendant glucuronic acid (PS-DGlu) was designed and systematically synthesized to be used as stabilizing agent in styrene miniemulsion polymerization; covalently incorporating oligo(p-phenylenevinylene) (OPV) based fluorophore to prepare PSG-OPV-n. This OPV fluorophore was incorporated with an aim to work as signal transducer while glucuronic acid on surface of PS nanobeads would act as water solubilizing moiety for PS to enable it to function as surfactant and also serve as interaction site for free bilirubin to facilitate non-covalent interaction via hydrogen bonding. Efficient energy transfer from OPV to bilirubin was observed owing to appreciable spectral overlap between emission of OPV and absorption of bilirubin. Visual color change from blue to bluish green was observed under UV lamp after addition of bilirubin into polymer. Selectivity of the sensor was checked among the pool of other interferences such as glucose, sucrose, metal ions, cholesterol and biliverdin. The limit of detection was found to be as low as 20 nM which is far less than the clinical range for causing jaundice (< 25 to > 50 µmol/L). Moreover, the developed sensor showed its effectiveness towards real time monitoring of free bilirubin in human serum.

 §      Sarabjot Kaur Makkad and S. K. Asha* Designed Amphiphilic Polystyrene as Surfactant for Oligo(pphenylenevinylene)-Incorporated PS Nanobeads and Visual Detection of Bilirubin in Human Blood Serum. ACS Appl. Polym. Mater. 2019, 1, 1230−1239 DOI: 10.1021/acsapm.9b00222

§      APPLICATION OF GLUCURONIC ACID FUNCTIONALIZED POLYSTYRENE NANOBEADS FOR BILIRUBIN DETECTION IN HUMAN SERUM. Complete filing. Asha S. K; Sarabjot Kaur 

 

CENTRE FOR EXCELLENCE IN THE FIELD OF PETROCHEMICALS:

Specialty polymers for Customized Additive Manufacturing