Name: fabricating reactive surfaces with brush-like and crosslinked films of azlactone-functionalized block co-polymers
Uploaded: 2018-06-30T13:00:00
Description: Watch this Scientific Journal Video about Fabricating Reactive Surfaces with Brush-like and Crosslinked Films of Azlactone-Functionalized Block Co-Polymers at JoVE.com

This research was supported by Kansas State University. A portion of this research was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences and U.S. Department of Energy.

1. PGMA-b-PVDMA Synthesis20
<ol>
	<li>Synthesis of PGMA macro-chain transfer agent (Macro-CTA)
	<ol>
		<li>Use a 250-mL round-bottom reaction &#64258;ask equipped with a polytetrafluoroethylene-coated magnetic stir bar.</li>
		<li>Combine 14.2 g of glycidyl methacrylate GMA (142.18 g/mol) with 490.8 mg of 2-cyano-2-propyl dodecyl trithiocarbonate (CPDT) (346.63 g/mol), and 87.7 mg of 2,2&#8242;-azobis (4-methoxy-2,4-dimethyl valeronitrile) (V-70) (308.43 g/mol) (molar ratio of CPDT: V-7...

This article presents three approaches to patterning PGMA-b-PVDMA, each with its set of advantages and drawbacks. The parylene lift-off method is a versatile method for patterning block co-polymers at micro to nanoscale resolution, and has been used as a deposition mask in other patterning systems33,34,35. Due to its relatively weak surface adhesion, the parylene stencil can be easily removed from the surface by sonicat...

Developing fabrication techniques that allow for versatile and precise control of chemical and biological surface functionality is desirable for a variety of applications, from capture of environmental contaminants to development of next generation biosensors, implants, and tissue engineering devices1,2. Functional polymers are excellent materials for tuning surface properties through &#34;grafting from&#34; or &#34;grafting to&#34; techniques3. These approaches allow for control of surface reactivity based on the chemical functionality of the monomer and molecular weight of the polymer4,5,6. Azlactone-based polymers have been intensely studied in this context, as azlactone groups rapidly couple with different nucleophiles in ring-opening reactions. This includes primary amines, alcohols, thiols and hydrazine groups, thereby providing a versatile route for further surface functionalization7,8. Azlactone-based polymer films have been employed in different environmental and biological applications including analyte capture9,10, cell culture6,11, and anti-fouling/anti-adhesive coatings12. In many biological applications, patterning azlactone polymer films at nano to micrometer length scales is desirable to facilitate spatial control of biomolecule presentation, cellular interactions, or to modulate surface interactions13,14,15,16,17,18. Therefore, fabrication methods should be developed to offer high pattern uniformity and well-controlled film thickness, without compromising chemical functionality19.
Recently, Lokitz et al. developed a PGMA-b-PVDMA block copolymer which was capable of manipulating surface reactivity. PGMA blocks couple to oxide-bearing surfaces, yielding high and tunable surface densities of azlactone groups20.&#160;Previously reported methods for patterning this polymer for creation of biofunctional interfaces used traditional top-down photolithography approaches that generated non-uniform polymer films with background regions contaminated with residual photoresist material, causing high levels of non-specific chemical and biological interactions21,22,23. Here, attempts to passivate background regions caused cross-reaction with azlactone groups, compromising polymer reactivity. Considering these limitations, we recently developed techniques for patterning brush (~90 nm) or highly crosslinked (~1-10 &#956;m) films of PGMA-b-PVDMA into chemically or biologically inert backgrounds in a manner that completely preserves the chemical functionality of the polymer24. These presented methods utilize parylene lift-off, interface-directed assembly (IDA), and custom microcontact printing (&#956;CP) techniques. Highly detailed experimental methods for these patterning approaches, as well as critical film characterizations and challenges and limitations associated with each technique are presented here in written and video format.

<table>
	<tbody>
		<tr>
			<td>Material</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol, &#8805; 99.5%</td>
			<td>Sigma-Aldrich</td>
			<td>459844</td>
			<td>-</td>
		</tr>
		<tr>
			<td>HCL, 1.019 N in H2O</td>
			<td>Fluka Analytical</td>
			<td>318949</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Acetone, &#8805; 99.5%</td>
			<td>Sigma-Aldrich</td>
			<td>320110</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Benzene, &#8805; 99.9%</td>
			<td>Sigma-Aldrich</td>
			<td>270709</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Isopropanol, ACS reagent, &#8805;99.5%</td>
			<td>Sigma-Aldrich</td>
			<td>190764</td>
			<td></td>
		</tr>
		<tr>
			<td>Hexane</td>
			<td>Fisher Chemical</td>
			<td>H292-4</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Argon</td>
			<td>Matheson Gas</td>
			<td>G1901175</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Tetrahydrofuran (THF), &#8805; 99.9%</td>
			<td>Sigma-Aldrich</td>
			<td>401757</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Pluronic F-127</td>
			<td>Sigma-Aldrich</td>
			<td>P2443</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Polydimethyl Siloxane (PDMS) Slygard 184</td>
			<td>Dow Corning</td>
			<td>4019862</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Trichloro (1H,1H,2H,2H-perfluorooctyl) silane (TPS), 97%</td>
			<td>Sigma-Aldrich</td>
			<td>448931</td>
			<td>It is toxic. Work with it under hood</td>
		</tr>
		<tr>
			<td>Anhydrous Chloroform, &#8805; 99%</td>
			<td>Sigma-Aldrich</td>
			<td>372978</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Positive Photoresist AZ1512</td>
			<td>MicroChemicals</td>
			<td>AZ 1512</td>
			<td>amber-red liquid, density 1.083 g/cm3, spin coating step should be done under the hood</td>
		</tr>
		<tr>
			<td>Developer AZ 300 MIF</td>
			<td>MicroChemicals</td>
			<td>AZ300 MIF</td>
			<td>clear colourless liquid with slight amine odor and density of 1 g/cm3</td>
		</tr>
		<tr>
			<td>1,2-Vinyl-4,4- dimethyl azlactone (VDMA)</td>
			<td>Isochem North America, LLC</td>
			<td>VDMA</td>
			<td>-</td>
		</tr>
		<tr>
			<td>2-cyano-2-propyl dodecyl trithiocarbonate (CPDT)</td>
			<td>Sigma-Aldrich</td>
			<td>723037</td>
			<td>-</td>
		</tr>
		<tr>
			<td>2,2&#8242;-Azobis (4methoxy-2,4-dimethyl valeronitrile) (V-70)</td>
			<td>Wako Specialty Chemicals</td>
			<td>CAS NO. 15545-97-8, EINECS No. 239-593-8</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Parylene N</td>
			<td>Specialty Coating Systems</td>
			<td>15B10004</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Parylene Coater</td>
			<td>Specialty Coating Systems</td>
			<td>SCS Labcoater (PDS 2010)</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Mask alignment system</td>
			<td>Neutronix Quintel</td>
			<td>NXQ8000</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Oxygen Plasma Etcher</td>
			<td>Oxford Instruments</td>
			<td>Plasma Lab System 100</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Surface Profilometer</td>
			<td>Veeco</td>
			<td>Dektak 150</td>
			<td>Scan type was standard hill. Scan duration and force were 120 s and 1 mg, respectively.</td>
		</tr>
		<tr>
			<td>Brightfield Upright Microscope</td>
			<td>Olympus Corporation</td>
			<td>BX51</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Oxygen Plasma&#160; Cleaner</td>
			<td>Harrick Plasma</td>
			<td>PDC-001-HP</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR)</td>
			<td>Perkin Elmer</td>
			<td>ATR-FTIR 100</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Atomic Force Microscopy (AFM)</td>
			<td>PicoPlus</td>
			<td>Picoplus atomic force microscope</td>
			<td>Veeco MLCT-E cantilevers with a 0.5 N/m spring constant. Scan speeds varied between 0.25 and 1 Hz.</td>
		</tr>
		<tr>
			<td>Scanning Electron Microscopy (SEM)</td>
			<td>Hitachi Science Systems Ltd., Tokyo, Japan</td>
			<td>-</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Rotary Tool Workstation</td>
			<td>Dremel</td>
			<td>Model 220-01</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Spin Coater</td>
			<td>Smart Coater</td>
			<td>SC100</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Vacuum Oven</td>
			<td>Yamato Scientific Co.</td>
			<td>PCD-C6(5)000)</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Size Exclusion Chromatography (SEC)</td>
			<td>Waters Alliance 2695 Separations Module</td>
			<td>720004547EN</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Refractive Index (RI) detector</td>
			<td>Waters</td>
			<td>Model 2414</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Photodiode Array Detector</td>
			<td>Waters</td>
			<td>Model 2996, 716001286</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Multi-angle Light Scattering (MALS) Detector</td>
			<td>Wyatt Technology</td>
			<td>miniDAWN TREOS II</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Viscometer</td>
			<td>Wyatt Technology</td>
			<td>Viscostar</td>
			<td>-</td>
		</tr>
		<tr>
			<td>PLgel 5 &#181;m mixed-C columns (300 x 7.5 mm)</td>
			<td>Agilent</td>
			<td>5 &#181;m mixed-C columns</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Ellipsometer</td>
			<td>J. A. Woollam</td>
			<td>alpha-SE</td>
			<td>Cauchy model, PGMA and PVDMA layers had refractive indices of 1.50 and 1.52 at 632 nm</td>
		</tr>
		<tr>
			<td>Ultrasonic Sonicator</td>
			<td>Fischer Scientific</td>
			<td>FS-110H</td>
			<td>-</td>
		</tr>
	</tbody>
</table>

fabricating reactive surfaces with brush-like and crosslinked films of azlactone-functionalized block co-polymers

In this paper, fabrication methods that generate novel surfaces using the azlactone-based block co-polymer, poly (glycidyl methacrylate)-block-poly (vinyl dimethyl azlactone) (PGMA-b-PVDMA), are presented. Due to the high reactivity of azlactone groups towards amine, thiol, and hydroxyl groups, PGMA-b-PVDMA surfaces can be modified with secondary molecules to create chemically or biologically functionalized interfaces for a variety of applications. Previous reports of patterned PGMA-b-PVDMA interfaces have used traditional top-down patterning techniques that generate non-uniform films and poorly controlled background chemistries. Here, we describe customized patterning techniques that enable precise deposition of highly uniform PGMA-b-PVDMA films in backgrounds that are chemically inert or that have biomolecule-repellent properties. Importantly, these methods are designed to deposit PGMA-b-PVDMA films in a manner that completely preserves azlactone functionality through each processing step. Patterned films show well-controlled thicknesses that correspond to polymer brushes (~90 nm) or to highly crosslinked structures (~1-10 &#956;m). Brush patterns are generated using either the parylene lift-off or interface directed assembly methods described and are useful for precise modulation of overall chemical surface reactivity by adjusting either the PGMA-b-PVDMA pattern density or the length of the VDMA block. In contrast, the thick, crosslinked PGMA-b-PVDMA patterns are obtained using a customized micro-contact printing technique and offer the benefit of higher loading or capture of secondary material due to higher surface area to volume ratios. Detailed experimental steps, critical film characterizations, and trouble-shooting guides for each fabrication method are discussed.

Contact angle measurements can be used to evaluate the functionalization of silicon with PGMA-b-PVDMA. Figure 1 depicts the contact angle of the silicon substrate during the different processing steps. Hydrophilic behavior of the plasma cleaned silicon substrate is shown in Figure 1B. The contact angle after polymer spin coating and annealing is 75&#176; &#177; 1&#176;(Figure 1C)...

Watch this Scientific Journal Video about Fabricating Reactive Surfaces with Brush-like and Crosslinked Films of Azlactone-Functionalized Block Co-Polymers at JoVE.com

Fabricating Reactive Surfaces with Brush-like and Crosslinked Films of Azlactone-Functionalized Block Co-Polymers

Surface fabrication methods for patterned deposition of nanometer thick brushes or micron thick, crosslinked films of an azlactone block co-polymer are reported. Critical experimental steps, representative results, and limitations of each method are discussed. These methods are useful for creating functional interfaces with tailored physical features and tunable surface reactivity.

In this paper, fabrication methods that generate novel surfaces using the azlactone-based block co-polymer, poly (glycidyl methacrylate)-block-poly (vinyl ...

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