Research

Core Polymer Characteristics:
- The core polymer can undergo methylation, leading to observable changes in its spectral characteristics.
- Upon methylation, there is a significant increase in the signal detected in the spectral area associated with metallic carbon nanotubes.

Raman Spectroscopy Application:
- Used to analyze carbon nanotubes before and after methylation of the polymer.
- Initial nanotubes show a strong metallic signal indicating they are metallic in nature.
- Nanotubes dispersed with unmethylated polymer do not show a signal in the metallic region, signifying that they are likely semiconducting.
- Post-methylation, the polymer causes a significant signal in the metallic region once again.

Methylation Implications:
- Methylation makes the polymer electron-poor, facilitating better dispersion of metallic carbon nanotubes.
- This leads to an expected enhancement in conductivity in films made from these materials.

Experimental Setup for Conductivity Measurement:
- A film was created to measure conductivity using a method called four-point probe measurement.
- This technique minimizes contact resistance in measurement and provides accurate conductivity readings for thin films.
Conductivity Results:
- Film made with semiconducting carbon nanotubes exhibits a conductivity of 3.1 imes 10^{-4} ext{ S/cm}.
- When the polymer is methylated, resulting in the dispersal of carbon nanotubes, the measured conductivity is four orders of magnitude higher, confirming the presence of higher conductivity materials.

Conductivity Comparison:
- Despite enrichment of metallic carbon nanotubes, their conductivity remains significantly lower than that of traditional metals like copper, gold, or silver.
- Metals typically conduct electricity about a million times better than the materials studied in this research.
- This presents a challenge for enhancing the conductivity of the polymer composite films.

Structure of Alkyl Chains:
- Alkyl chains were introduced to ensure the solubility of the polymer.
- These chains extend outward from the carbon nanotubes, resembling hairs, thus inhibiting effective contact between nanotubes necessary for conductivity.
- Close contact between nanotubes is essential to allow electron tunneling and conductivity between them.
- The insulating nature of the side chains creates a barrier to effective connectivity among carbon nanotubes.

Research Objective for Cleavable Side Chains:
- Previous studies indicated a need to improve conductivity by allowing better contact between carbon nanotubes.
- The aim was to design side chains that could be cleaved thermally, removing the insulating barriers once they are no longer needed.
Cleavable Side Chain Structure:
- A graduate student designed a molecule featuring a thermally cleavable carbonate group.
- Heating to approximately 200-170 degrees Celsius causes the carbonate group to decompose, facilitating the removal of the insulating side chain.

Procedure for Thermogravimetric Analysis:
- A sensitive balance is used to measure the mass of a polymer sample as it is heated to observe thermal stability and decomposition.
Data Interpretation from Thermograms:
- The thermogram displays mass loss at approximately 150 degrees Celsius, confirming the breakdown of the cleavable side chain.
- The control sample lacking the cleavable side chains does not show mass loss in this temperature range, confirming the specific removal of side groups in treated samples.
Further Heating Results:
- Continued heating to 400 degrees Celsius results in the degradation of the remaining polymer structure, underscoring the stability of the chemical bonds in the molecule until the specific temperature is reached.