Department of Chemistry, the University of North Carolina at Chapel Hill, NC, USA.
Department of Biomedical Engineering, UNC, Chapel Hill, NC, USA.
Analyst. 2016 Nov 28;141(24):6521-6532. doi: 10.1039/c6an01448h.
The ethylene/norbornene content within cyclic olefin copolymer (COC) is well known to affect the chemical and physical properties of the copolymer, such as the glass transition temperature (T) and transparency. However, no work has been reported evaluating the effects of the ethylene/norbornene content on the surface properties of COC following UV/O or O plasma activation. Activation with either O plasma or UV/O is often used to assist in thermal assembly of fluidic devices, increasing the wettability of the surfaces, or generating functional scaffolds for the attachment of biological elements. Thus, we investigated differences in the physiochemical surface properties of various ethylene/norbornene compositions of COC following activation using analytical techniques such as water contact angle (WCA), ATR-FTIR, XPS, TOF-SIMS, UV-VIS, AFM and a colorimetric assay utilizing Toluidine Blue O (TBO). Results showed that increased norbornene content led to the generation of more oxygen containing functionalities such as alcohols, ketones, aldehydes and carboxyl groups when activated with either UV/O or O plasma. Specifically, COC with ∼60% norbornene content showed a significantly higher -COOH functional group density when compared to COC with a 50% norbornene content and COC with a 35% norbornene content following UV/O or O plasma activation. Furthermore, COC with large norbornene contents showed a smaller average RMS roughness (0.65 nm) when compared to COC containing low norbornene contents (0.95 nm) following activation making this substrate especially suited for nanofluidic applications, which require smooth surfaces to minimize effects arising from dielectrophoretic trapping or non-specific adsorption. Although all COC substrates showed >90% transparency at wavelengths >475 nm, COC possessing high norbornene contents showed significantly less transparency at wavelengths below 475 nm following activation, making optical detection in this region difficult. Our data showed distinct physiochemical differences in activated COC that was dependent upon the ethylene/norbornene content of the thermoplastic and thus, careful selection of the particular COC grade must be considered for micro- and nanofluidics.
环烯烃共聚物 (COC) 中的乙烯/降冰片烯含量众所周知会影响共聚物的化学和物理性质，例如玻璃化转变温度 (T) 和透明度。然而，尚未有研究报道评价乙烯/降冰片烯含量对 COC 经 UV/O 或 O 等离子体激活后的表面性质的影响。使用 O 等离子体或 UV/O 激活通常用于辅助流体装置的热组装，增加表面的润湿性，或生成用于生物元件附着的功能支架。因此，我们使用诸如水接触角 (WCA)、ATR-FTIR、XPS、TOF-SIMS、UV-VIS、AFM 和利用甲苯胺蓝 O (TBO) 的比色测定等分析技术，研究了 COC 的不同乙烯/降冰片烯组成在经激活后的物理化学表面性质的差异。结果表明，增加降冰片烯含量会导致在用 UV/O 或 O 等离子体激活时生成更多含氧官能团，如醇、酮、醛和羧基。具体而言，与含有 50%降冰片烯含量的 COC 和含有 35%降冰片烯含量的 COC 相比，含有约 60%降冰片烯含量的 COC 在经 UV/O 或 O 等离子体激活后显示出明显更高的 -COOH 官能团密度。此外，与含有低降冰片烯含量的 COC（0.95nm）相比，高降冰片烯含量的 COC 在激活后具有更小的平均 RMS 粗糙度（0.65nm），这使其特别适合用于需要光滑表面以最小化由介电泳捕获或非特异性吸附引起的影响的纳流控应用。尽管所有 COC 基材在波长大于 475nm 时都显示出 >90%的透明度，但在经激活后，具有高降冰片烯含量的 COC 在波长低于 475nm 时显示出明显较低的透明度，使得在该区域进行光学检测变得困难。我们的数据显示，经激活的 COC 存在明显的物理化学差异，这取决于热塑性塑料中的乙烯/降冰片烯含量，因此，必须仔细选择特定的 COC 等级，以用于微纳流控。
