By,K Hayagreev V Sarma,IISER-TVM.24th June,2015.

Resonators based dielectric parameters change in

Polyurethane as an exordial for sensor application

Research MentorDr K C James Raju

ProfessorSchool of Physics

University of Hyderabad

At,

AbstractCarbowax-1000 a conducting polymer was found to give appreciable results in detection of explosive vapours in sensor applications. Coating of Carbowax-1000 over fused silica substrates using solvents such as Acetone, Chloroform, had less temperature stability. So, Carbowax-1000 is being used to form a Polyurethane. As a prelude dielectric parameters change was observed for HTPB-IPDI-PU (Hydroxyl-terminated polybutadiene – Isophorone diisocyanate – Polyurethane) when interacted with Toluene, THF, etc. using SPDR (Split Post Dielectric Resonator).HTPB-IPDI-PU was synthesized and spin coated to obtain thin films of ≈2µm and cured for 5 days at 323 K. Initial frequency and quality factor value (Q) value were measured for bare substrate and polymer film coated substrate. Shift in resonance frequency and Q value was measured after placing Toluene, THF, etc. in µLs over the polymer film. Shift in resonance frequency ranged from 1-100 MHz for different solvents. Considerable Q value changes were also observed.

Polymer Synthesis

Spin Coating

Dielectric Parameters Measurement using SPDR

Outline of my Work

SPDR (Split Post Dielectric Resonator)

The SPDR provides an accurate technique for measuring the complex permittivity of dielectric and ferrite substrates and thinfilms at a single frequency point in the frequency range of 1 to 20GHz.

Besides the SPDR fixture, a vector network analyser such as the PNA or PNA-L and software package 85071E option 300, are required for the measurement. The measurement is automatic and easy to perform.

Advantages:• superior accuracy compared to other methods

• ability to measure low loss materials.

• convenient, fast, and non-destructive measurement of substrates, printed circuit boards, and even thin films.Geometry and arrangement:

Spin Coating:

Fused Silica Substrates

Spin coating is a procedure used to deposit uniform thin films to flat substrates. Usually a small amount of coating material is applied on the centre of the substrate, which is either spinning at low speed or not spinning at all. The substrate is then rotated at high speed in order to spread the coating material by centrifugal force. A machine used for spin coating is called a spin coater, or simply spinner.

Factors on which thickness of the film mainly depends:

Ѡ angular speed(in rpm)

Viscosity of the Liquid

Evaporation speed of the liquid.

Time of Rotation

Substrate Cleaning:

Ultasonicate for 5 min in

Acetone

Ultasonicate for 5 min in 2-propanol

Ultasonicate for 5 min in

Distilled water

Blow Nitrogen

Polymer Synthesis

PolyurethanePolyurethane (PUR or PU) is a polymer composed of a chain of organic units joined by carbamate (urethane) links. While most polyurethanes are thermosetting polymers that do not melt when heated, thermoplastic polyurethanes are also available. Polyurethane polymers are traditionally and most commonly formed by reacting a di- or polyisocyanate with a polyol.

Hydroxyl Terminated (poly) butadiene

Isophorone diisocyanate

Urethane Functional

group

HTPB-IPDI-PU

Polyurethane Synthesis: A 3 neck round bottom flask was

taken and HTPB was dissolved in chloroform in it.

The middle neck was used for mechanical stirring and one of the side necks for nitrogen with the other for adding reactants.

IPDI and Catalyst DBTDL was added in calculated amounts for cyanide alcohol ratio to be 1.

Then the mechanical stirring was continued for 3 hours for optimum results.

Polymer prepared was then immediately spin coated on substrates of our choice ( Fused silica substrates).

Polymer coated substrates were cured at 70° C for 5 days.

HTPB-IPDI-PU Substrate No.

RPM on spin coater

Trial 1(Angstroms)

Trial 2(Angstroms)

Trial 3(Angstroms)

1 1000 17088 17593  --

2 1000 16816 16694  --

3 2000 16644 16696  --

4 2000 22601 20824  --

5 3000 15509 16099  --

6 3000 29261 33360 32380

7 4000 48461 56611 44031

8 5000 38941 42619  --

9 6000 17079 17329  --

Thickness of HTPB-IPDI-PU on Fused Silica Substrates measured using

Thickness of Each thin film was less than 5 µm

Profilometer

  Initial Resonance Frequency(G Hz)

Q value

Pure fused silica substrate

10.009 10406

Sample 4 10.006 10412

Toluene 2 µL

10.005 10046

  Initial Resonance Frequency(G Hz)

Q value

Pure fused silica substrate

10.006 10616

Sample 7 9.9988 9091.8

THF 2 µL 9.9980 8541.8

  Initial Resonance Frequency(G Hz)

Q value

Pure fused silica substrate

10.006 10616

Sample 8 10.012 9262

THF 16 µL 9.9828 2006

  Initial Resonance Frequency(G Hz)

Q value

Pure fused silica substrate

10.009 10406

Sample 9 10.005 9005

TNT in Acetonitrile 4 µL

9.988 2009

SPDR Measurements for different substances on Polyurethane

Acknowledgments:• Prof K C James Raju, SoP, UoH. for his valuable

suggestions and support.• My sincere thanks to Mr E Sivanagi Reddy, Mr Andrews

Joseph, SoP, UoH.• A very special thanks to Mr Billa Narasimha Rao,

ACRHEM, UoH for his valuable guidance and support for polymer synthesis.

• Ms Sandhya, Centre of Nanotechnology, UoH.

References:• Niranjan Sahu, B Parija and S Panigrahi, Indian J. Phys. 83

(4) 493-502 (2009)• Malkappa, K.; Jana, T. Ind. Eng. Chem. Res., 2013, 52,

12887–12896.• Agilent Split Post Dielectric Resonators for Dielectric

Measurements of Substrates Application Note

Thank You !!