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«by CARRIE ELLEN SCHINDLER DERRICK R. DEAN, CHAIR SHANE AARON CATLEDGE NITIN CHOPRA VINOY THOMAS YOGESH VOHRA A DISSERTATION Submitted to the graduate ...»

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FABRICATION AND CHARACTERIZATION OF FUNCTIONALIZED POLYMER

SYSTEMS USING DIP-PEN NANOLITHOGRAPHY

by

CARRIE ELLEN SCHINDLER

DERRICK R. DEAN, CHAIR

SHANE AARON CATLEDGE

NITIN CHOPRA

VINOY THOMAS

YOGESH VOHRA

A DISSERTATION

Submitted to the graduate faculty of The University of Alabama at Birmingham, in partial fulfillment of the requirements for the degree of Doctor of Philosophy

BIRMINGHAM, ALABAMA

2014 Copyright by

CARRIE ELLEN SCHINDLER

2014

FABRICATION AND CHARACTERIZATION OF FUNCTIONALIZED POLYMER

SYSTEMS USING DIP-PEN NANOLITHOGRAPHY

CARRIE ELLEN SCHINDLER

MATERIALS ENGINEERING

ABSTRACT

As more technology shifts from the microscale to the nanoscale, the demand for new fabrication and characterization methods to investigate material properties on the nanoscale significantly increases. Dip-pen nanolithography is an innovative printing technique with the precision to deposit a multitude of inks with nanoscale dimensions on a variety of substrates. This bottom-up approach of high-throughput printing has enabled the study of nanomaterials spanning the gamut of disciplines from nanoelectronics to single-cell interactions to drug delivery. However, the scalability and reproducibility of the dip-pen nanolithography platform has yet to reach full potential in terms of large- scale material production. Specifically, the dip-pen nanolithography platform can address some of the challenges that hinder the development of two polymer systems, tissue engineering polymer systems and electroactive polymer systems. This work utilizes dip- pen nanolithography as a basis for creating nanocomposites for tissue engineering and ‘smart’ materials by the functionalization and characterization of novel polymer blend scaffolds and electroactive polymer systems. Additionally, this work enhances the application areas of the dip-pen nanolithography system with specific impacts on nanotechnology and the advancement of unique polymer systems.

The work begins with electrospinning polymer blends of polycaprolactone and polyglyconate for the first time. The mechanical, rheological, thermal and morphological behaviors of the electrospun blends provide guidance for the design and optimization of iii hybrid scaffold systems. This provided a matrix for dip-pen nanolithography patterning with hydroxyapatite inks. Nanoparticle based inks of hydroxyapatite were designed for specific use with dip-pen nanolithography. The inks were tested in terms of stability, dispersion, and accuracy of patterning to determine the optimal formulation for high throughput printing onto electrospun scaffolds.

In addition to tissue engineering applications, this work also focused on developing new techniques to pattern carbon nanotubes on electroactive polymer films in the nanoregime. Carbon nanotubes inks were formulated as a nanoparticle-based ink for dip-pen nanolithography patterning. These formulations led to the first reported direct deposition of multi-walled carbon nanotubes by dip-pen nanolithography with printed features ranging from 400 nm to 4 μm. These carbon nanotube features were printed onto polymer films as ongoing work to develop electroactive polymer composites using dippen nanolithography.

Keywords: Electrospun polyglyconate, electroactive polymer composites, dip-pen nanolithography, carbon nanotube inks, nanohydroxyapatite inks.

–  –  –

 My mentor and friend, Dr. Derrick Dean for allowing me to express my creativity and scientific curiosity while supporting my research endeavors with his deep compassion. I couldn’t have found a mentor for my personality and work ethic to drive me to better myself. He is truly a remarkable person that has shaped me into a better person throughout my time at UAB.

 The UAB REU Physics program and Dr. Vohra for giving me an opportunity to conduct research as an undergraduate in 2008. Without this opportunity, I would not have the passion for my research nor the insight into what UAB offers.

 My family, my fiancé, and my friends who have supported me blindly through this process. Even though I may get frustrated with the million times they asked me when I was going to graduate, they have been there for me.

 My UAB colleagues who have helped me when I was struggling, brought me a cherry coke, and gave me access to the instruments I needed to complete my dissertation. Thank you to the polymer lab group members past, present, and

–  –  –

 The Department of Materials Science and Engineering, especially Vernon Merchant, Cynthia Barham, and Robin Mize, whose help does not go unnoticed.

 My committee and other mentors along the way who have offered me valuable

–  –  –





Abstract

DEDICATION

ACKNOWLEDGMENTS

LIST OF TABLES

LIST OF FIGURES

LIST OF ABBREVIATIONS

1. INTRODUCTION

2. LITERATURE REVIEW

2.1 Tissue engineering polymer systems

2.2 Hydroxyapatite

2.3 Electroactive polymer systems

2.4 Carbon nanotubes

2.5 Dip-pen nanolithography

3. SPECIFIC AIMS

–  –  –

4. MATERIALS AND EXPERIMENTAL METHODS

4.1 Biodegradable polymers

4.2 Nano-Hydroxyapatite ink formulation

4.3 Carbon nanotube ink formulation

4.4 Electrospinning

4.5 Microscopy

4.6 Thermal Analysis

4.7 Mechanical Testing

vii 4.8 In-vitro degradation

4.9 Spectroscopy

4.10 Rheology

4.11 Nanoparticle ink stability

4.12 DPN printing

5. ELECTROSPUN POLYCAPROLACTONE/POLYGLYCONATE BLENDS:

MISCIBILITY, MECHANICAL BEHAVIOR, AND DEGRADATION............20

6. CONTROLLED PATTERNING OF NANO-HYDROXYAPATITE BY DIPPEN LITHOGRAPHY

7. CARBON NANOTUBE INKS FOR DIRECT PATTERNING BY DIP-PEN

NANOLITHOGRAPHY

8. FUTURE DIRECTIONS

9. CONCLUSIONS

10. REFERENCES

–  –  –

ELECTROSPUN POLYCAPROLACTONE/POLYGLYCONATE BLENDS:

MISCIBILITY, MECHANICAL BEHAVIOR, AND DEGRADATION

1 Comparison of thermal properties of PCL and Maxon electrospun blends to pure components obtained by first scan of DSC

2 Tensile properties of electrospun Maxon and PCL blends (n=5)

3 Modulus of elasticity as a function of aging time

–  –  –

1 Average particle diameter measurements of nanoHA solutions by dynamic-light scattering and SEM analysis

–  –  –

1 Zeta potential measurements (n=3) for MWCNT solutions as a function of concentrations and viscosities

–  –  –

1 Schematic of electrospinning set-up to obtain randomly aligned polymer fibers.

2 The profiles of an electroactive polymer film indicating the change from

A) a flat orientation to B) a deformed state as a result of applying electrical stimulus. (Adapted from Ouyang et al.)

3 Schematic of the transport of molecular inks to a substrate through the water meniscus. (Adapted from Piner et al.)

ELECTROSPUN POLYCAPROLACTONE/POLYGLYCONATE BLENDS:

MISCIBILITY, MECHANICAL BEHAVIOR, AND DEGRADATION

1 SEM images electrospun 3:1 PCL/Maxon (left) and 3:1 Maxon/PCL (right) blend scaffolds. (Scale bar is 50 microns)

2 Fiber diameter distribution of electrospun nanofiber scaffolds consisting of neat PCL, neat Maxon, 3:1 PCL/Maxon, and 3:1 Maxon/PCL.

100 measurements were recorded for each sample

3 DSC first heat scans of the Maxon and PCL blends in comparison to the neat components. The changes in enthalpies of melting indicate the partial miscibility of the blends.

4 DSC first heat scans of 3:1 Maxon/PCL samples indicating the complete etching of the PCL component after 5 hour in DCM

5 Representative SEM images showing the effect on fiber morphology before (left) and after (right) etching the PCL with DCM on the 3:1 Maxon/PCL scaffolds. (Scale bar is 5 microns)

6 DSC thermograms of the 3:1 Maxon/PCL blend after annealing at the indicated temperatures and quenching. The arrow indicates increased phase separation with increasing annealing temperature

–  –  –

8 Viscoelastic properties of PCL/Maxon blends shown as storage modulus as a function of frequency of loading obtained by DMA master curve time-temperature-superposition

9 Representative SEM images showing the hydrolytic degradation effect on electrospun PCL, Maxon, 3:1 PCL/Maxon, and 3:1 Maxon/PCL, respectively at 0 day exposure (A-D) and 42 days exposure (E-H) in phosphate buffered saline at 37°C. (Scale bar is 20 microns)

10 FT-IR ATR spectra of A) the comparison of neat PCL, neat Maxon, and the blended scaffolds at 0 days aging. The effects of aging on the

B) Maxon, C) 3:1 PCL/Maxon, and D) 3:1 Maxon/PCL scaffolds showing hydrolytic degradation from exposure to phosphate buffered saline for 0 days, 21 days, and 42 days. (The asterisks indicate the wavenumbers signifying the breakdown of amorphous PGA units in the Maxon)

11 Degradation effects on enthalpy of fusion as a function of aging time in PBS at 37°C. Solid lines represent the PCL component and dashed lines represent the Maxon component of enthalpy

–  –  –

1 Average viscosity measurements at 25°C as a function of glycerol content for nanoHA inks, showing the target viscosity range for DPN printing (n=6)

2 Dynamic light-scattering particle size distributions of nanoHA solutions as a function of increasing glycerol content from 0 – 90% glycerol

3 SEM images showing the changes in nanoHA distribution of A) as received powder and nanoHA solutions with B) 0% glycerol C) 30% glycerol and D) 50% glycerol. (Scale bar is 1 micron)

4 Turbidity measurements as a function of time after sonication showing the stability of the nanoHA inks with increasing glycerol content

5 Measurements of dot diameter and z-height from AFM topography images averaged over 3 x 3 DPN printed arrays (n=5) as a function of dwell time..........68 6 AFM phase images of DPN printed dots with increasing dwell times of A) 1 second B) 3 seconds and C) 5 seconds indicating the presence of nanoHA particles within each dot. (Scale bar is 1 micron)

xi 7 SEM images of A-B) electrospun fibers on a SiO2 substrate indicating the presence of nanoHA particles printed by DPN. (Scale bar is 10 microns) The nanoHA particles were confirmed with C) the EDS spectrum of the printed features.

8 SEM images of aligned electrospun scaffolds A) before and B) after DPN printing, indicating the presence of nanoHA particles along a single fiber. (Scale bar is 5 microns) The nanoHA particles were confirmed with C) the EDS spectrum of the printed features.

–  –  –

1 Viscosity measurements at 25°C as a function of glycerol content for 1 wt% Triton X-100 in isopropyl alcohol, showing the target viscosity range for DPN printing (n=6)

2 A) Absorbance and emission spectra of the 0.01 mg/mL MWCNT solutions indicating the Stokes shift and deconvolution of absorbance peaks. B) The effect of Triton X-100 surfactant on fluorescence spectra of the MWCNT solutions

3 Evaluation of dispersion based on the comparison of MWCNT solution concentrations on fluorescence intensity with increasing viscosities by adding 30 – 50 w/v glycerol. SEM images at 3000X magnification show visual bundling at lower intensities

4 Turbidity measurements as a function of times after sonication showing the stability of A) 0.01 mg/mL, B) 0.05 mg/mL, and C) 0.1 mg/mL MWCNT solutions with increasing amounts of 0, 30, 40, and 50 w/v glycerol

5 AFM topography images of arrays printed with A) 3 second dwell times and B) 5 second dwell times. Measurements of dot diameter and z-height are shown for each corresponding dwell time

6 AFM phase images of the 5 second dwell individual dots printed with

a) a control solution without MWCNTs b) 30 w/v glycerol c) 40 w/v glycerol and d) 50 w/v glycerol showing the presence of MWCNTs within the dots

7 Raman spectra for individual DPN printed dots using a 3 second dwell time with the 0.05 mg/mL MWCNT solutions of a) 30 w/v glycerol b) 40 w/v glycerol and c) 50 w/v glycerol

–  –  –

1 Electrostatic force microscopy images showing the topographic changes in the PVDF/CNT film by applying a) 2 V and b) 10 V stimulus.

–  –  –

PVDF Poly(vinylidene fluoride) SEM Scanning electron microscopy Tg Glass transition temperature Tm Melting temperature TMC Trimethylene carbonate TX-100 Triton X-100

–  –  –

Tissue engineering is an emergent field of research aimed at providing alternative solutions to combat diseases. The main areas of research involve the treatment of heart disease, diabetes, and complications from cancer [1]. Most recently, novel synthetic polymers or nature-derived materials have been proposed in combination with nanotechnology to create composite structures for specific tissues in the body [1-5].



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