Controllable Cross-Linking of Vapor-Deposited Polymer Thin Films and Impact on Material Properties

Blockage of pipelines by formation and accumulation of clathrate hydrates of natural gasses (also called gas hydrates) can compromise project safety and economics in oil and gas operations, particularly at high pressures and low temperatures such as those found in subsea or arctic environments. Cyclopentane (CyC5) hydrate has attracted interest as a model system for studying natural gas hydrates, because CyC5, like typical natural gas hydrate formers, is almost fully immiscible in water; and thus CyC5 hydrate formation is governed not only by thermodynamic phase considerations but also kinetic factors such as hydrocarbon/water interfacial area and mass & heat transfer, as for natural gas hydrates. We present a macroscale investigation of the formation and adhesion strength of CyC5 hydrate deposits on bilayer polymer coatings with a range of wettabilities. The polymeric bilayer coatings are developed using initiated chemical vapor deposition (iCVD) of a mechanically-robust and 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 densely-cross-linked polymeric base layer (poly-divinyl benzene or pDVB) that is capped with a covalently-attached thin hydrate-phobic fluorine-rich top layer (polyperfluorodecylacrylate or pPFDA). The CyC5 hydrates are formed from CyC5-in-water emulsions, and differential scanning calorimetry (DSC) is used to confirm the thermal dissociation properties of the solid hydrate deposits. We also investigate the adhesion of the CyC5 hydrate deposits on bare and bilayer polymer-coated silicon and steel substrates.Goniometric measurements with drops of CyC5-in-water emulsions on the coated steel substrates exhibit advancing contact angles of 148.3º ± 4.5º and receding contact angles of 142.5º ± 9.8º, indicating the strongly emulsion-repelling nature of the iCVD coatings. The adhesion strength of the CyC5 hydrate deposits reduced from 220±45 kPa on rough steel substrates to 20±17 kPa on the polymer-coated steel substrates. The measured strength of CyC5 hydrate adhesion is found to correlate very well with the work of adhesion between the emulsion droplets used to form the CyC5 hydrate and the underlying substrates.

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“…40 This resulted in deposition of a densely cross-linked DVB polymer (pDVB) network with the desired thickness (in the range of 200 nm -1 µm).…”

Section: Resultsmentioning

confidence: 99%

Investigation into the Formation and Adhesion of Cyclopentane Hydrates on Mechanically Robust Vapor-Deposited Polymeric Coatings

Sojoudi¹,

Walsh

Gleason³

et al. 2015

Langmuir

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“…The in situ graing in process A was repeated once to ensure good surface coverage of graing sites. In process B, DVB, N 2 , and TBPO were introduced simultaneously to the low pressure reactor similar to the traditional iCVD 41 polymerization process while the lament and the substrate were kept at T f ¼ 250 C and T s ¼ 30 C, respectively.…”

Section: 28mentioning

confidence: 99%

“…41 The elastic modulus and hardness of the densely cross-linked pDVB network were E ¼ 15.7 AE 1.5 GPa and H ¼ 390.1 AE 4.0 MPa, respectively. These values are signicantly higher than the elastic modulus (E ¼ 8.2 AE 2.1 GPa) and the hardness (H ¼ 131.0 AE 5.7 MPa) of the pPFDA lm.…”

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confidence: 96%

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Linker-free grafting of fluorinated polymeric cross-linked network bilayers for durable reduction of ice adhesion

2015

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Thin films of bilayer poly(divinyl benzene) p(DVB)/poly(perfluorodecylacrylate) (p-PFDA) are synthesized via iCVD on steel and silicon substrates. Nanomechanical measurements reveal that the elastic modulus and hardness of the films are enhanced through the bilayer structure and that the adhesion of the films to the substrate is improved via in situ grafting mechanism. The strength of ice adhesion to the treated surfaces is reduced more than six-fold when the substrates are coated with these bilayer polymer networks. 9 Icing can decrease efficiency in power production, result in mechanical and/or electrical failure, impact monitoring and control, and generate safety hazards.2,3,5,7 Active deicing methods that are employed to melt and break previously formed ice layers necessitate increased design complexity, may have detrimental environmental consequences, and require substantial power input for operation.10,11 Passive methods have recently been employed to protect exposed surfaces using icephobic coatings with characteristics designed to retard the formation of ice and facilitate the removal of ice deposits.3,9,12-22 Such coatings have been developed using solgel systems containing uorinated compounds and low surface energy rubbers, 20 lubricant-impregnated textured surfaces, 4 via hydrothermal reaction method, 23 low-pressure plasma polymerization, 24 and phase-separation methods. 7 However, a need remains for deposition methods that produce durable and mechanically-robust coatings over the large areas with enhanced adhesion to textured/rough surfaces that are commonly encountered in real world applications.In the present work, we have designed and synthesized for the rst time a mechanically-robust bilayer consisting of a thick and dense polymer base layer that is highly cross-linked and then capped with a covalently-attached thin icephobic uorine-rich top layer. We believe that the presence of a highly cross-linked polymer layer underneath a very thin u-oropolymer cap acts as a steric barrier resisting local surface reorganization, forcing the uorinated groups to remain on the surface even under wet conditions (Fig. S1, ESI †). In addition, the mechanical properties (for example the elastic modulus and hardness) of these customized bilayer polymer networks can be signicantly enhanced. Conceptual insightsIce formation and accumulation on surfaces can result in severe problems for solar photovoltaics, offshore oil platforms, wind turbines, and aircra. Practical adoption of icephobic surfaces requires mechanical robustness and stability under the harsh real-world environments. Here we design an icephobic surface using a bilayer strategy, optimizing the base layer for mechanical properties, while the top layer provides the desired high receding water contact angle (WCA). Both layers are formed sequentially by initiated chemical vapor deposition (iCVD) in the same reaction chamber. The iCVD polymerization of divinyl benzene (DVB) yields a cross-linked hydrocarbon base layer which is capped with an ultrathi...

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“…[30] This resulted in deposition of a densely cross-linked DVB polymer (pDVB) with the desired thickness (in the range of 200 nm -1 µm).…”

Section: Resultsmentioning

confidence: 99%

Designing Durable Vapor‐Deposited Surfaces for Reduced Hydrate Adhesion

Sojoudi

Walsh

Gleason

et al. 2015

Adv Materials Inter

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The formation and accumulation of clathrate hydrates inside oil and gas pipelines causes severe problems in deep-sea oil/gas operations. In the present work, durable and mechanically-robust bilayer poly-divinyl benzene (pDVB)/poly(perfluorodecylacrylate) (pPFDA) coatings are developed using initiated chemical vapor deposition (iCVD) to reduce the adhesion strength of hydrates to underlying substrates. Tetrahydrofuran (THF) dissolved in water with a wt. % concentration of 0-70 is used to study the formation of hydrates and their adhesion strength. Goniometric measurements of water droplets on the coated substrates exhibit advancing contact angles of 157.8º ± 2.3º and receding contact angles of 131º ± 8º, whereas 70 wt. % THF in water droplets present advancing angle of 85.1º ± 6.1º and receding angle of 48.5º ± 4.9º. The strength of hydrate adhesion experiences a ten-fold reduction when substrates are coated with these iCVD polymers: from 1050±250 kPa on bare substrates to 128±100 kPa on coated ones. The impact of subcooling temperature and time on the adhesion 2 strength of hydrate on substrates is also studied. The results of this work suggest that the THF-water mixture repellency of a given substrate can be utilized to assess its hydrate-phobic behavior; hence, it opens a pathway for studying hydrate-phobicity.

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Controllable Cross-Linking of Vapor-Deposited Polymer Thin Films and Impact on Material Properties

Cited by 48 publications

References 73 publications

Investigation into the Formation and Adhesion of Cyclopentane Hydrates on Mechanically Robust Vapor-Deposited Polymeric Coatings

Investigation into the Formation and Adhesion of Cyclopentane Hydrates on Mechanically Robust Vapor-Deposited Polymeric Coatings

Linker-free grafting of fluorinated polymeric cross-linked network bilayers for durable reduction of ice adhesion

Designing Durable Vapor‐Deposited Surfaces for Reduced Hydrate Adhesion

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