Rengifo Hernán R, Chen Lu, Grigoras Cristian, Ju Jingyue, Koberstein Jeffrey T
Department of Chemical Engineering, Columbia University, 500 West 120th Street, MC4721, New York, New York 10027, USA.
Langmuir. 2008 Jul 15;24(14):7450-6. doi: 10.1021/la800038j. Epub 2008 Jun 18.
There are few existing methods for the quantitative functionalization of surfaces, especially for polymeric substrates. We demonstrate that alkyne end-functional diblock copolymers can be used to provide precise areal densities of reactive functionality on both hard (e.g., glass and silicon oxide) and soft (i.e., polymeric) substrates. Alkyne functionality is extremely versatile because the resultant functional surfaces are reactive toward azide functional molecules by Sharpless click chemistry. Spin-coated films of alpha-alkyne-omega-Br-poly( tert-butylacrylate- b-methylmethacrylate) (poly( tBA-MMA)) spontaneously self-assemble on the aforementioned substrates to present a surface monolayer of PtBA with a thickness in the range of 1 to 9 nm. The PMMA block physisorbs to provide multivalent anchoring onto hard substrates and is fixed onto polymer surfaces by interpenetration with the substrate polymer. The areal density of alkyne functional groups is precisely controlled by adjusting the thickness of the block copolymer monolayer, which is accomplished by changing either the spin coating conditions (i.e., rotational speed and solution concentration) or the copolymer molecular weight. The reactivity of surface-bound alkynes, in 1,3-dipolar cycloaddition reactions or by so-called "click chemistry", is demonstrated by covalent surface immobilization of fluorescently labeled azides. The modificed surfaces are characterized by atomic force microscopy (AFM), contact angle, ellipsometry, fluorescent imaging and angle-dependent X-ray photoelectron spectroscopy (ADXPS) measurements. Microarrays of covalently bound fluorescent molecules are created to demonstrate the approach and their performance is evaluated by determining their fluorescence signal-to-noise ratios.
目前用于表面定量功能化的方法很少，尤其是对于聚合物基材。我们证明，炔烃端基功能化的二嵌段共聚物可用于在硬（如玻璃和氧化硅）和软（即聚合物）基材上提供精确的反应性功能的面密度。炔烃功能极为通用，因为通过Sharpless点击化学，所得功能表面对叠氮化物功能分子具有反应性。α-炔烃-ω-溴-聚（丙烯酸叔丁酯-嵌段-甲基丙烯酸甲酯）（聚（tBA-MMA））的旋涂膜在上述基材上自发自组装，形成厚度在1至9纳米范围内的PtBA表面单层。PMMA嵌段通过物理吸附在硬基材上提供多价锚定，并通过与基材聚合物互穿固定在聚合物表面。通过调节嵌段共聚物单层的厚度来精确控制炔烃官能团的面密度，这可以通过改变旋涂条件（即转速和溶液浓度）或共聚物分子量来实现。通过荧光标记叠氮化物的共价表面固定，证明了表面结合炔烃在1,3-偶极环加成反应或所谓“点击化学”中的反应性。通过原子力显微镜（AFM）、接触角、椭偏仪、荧光成像和角度分辨X射线光电子能谱（ADXPS）测量对改性表面进行表征。创建共价结合荧光分子的微阵列以证明该方法，并通过确定其荧光信噪比来评估其性能。
