Surface-initiated Ring-opening Metathesis Polymerization Research Articles

Surface-Initiated, Ring-Opening Metathesis Polymerization: Formation of Diblock Copolymer Brushes and Solvent-Dependent Morphological Changes

In this article, we report the formation of diblock copolymer brushes on a gold surface by surface-initiated, ring-opening metathesis polymerization (SI-ROMP) with the newly developed ruthenium catalyst [(H2IMes)(3-Br-py)2(Cl)2Ru=CHPh]. Taking advantage of the highly improved activity of the ruthenium catalyst and the rapid initiation step of ROMP, we successfully formed thin films of well-defined block copolymers with 5-norbornene-2-endo,3-endo-dimethanol and norbornene carboxylic acid methyl esters (44:56 endo/exo). The catalyst was found to be active enough to polymerize endo isomers of norbonene derivatives from the surface as well as to form diblock copolymer brushes. SI-ROMP of diblock copolymers from the surface was confirmed by ellipsometry, infrared spectroscopy, and X-ray photoelectron spectroscopy. After the formation, the polymer-grafted substrates were immersed in various solvents, and the selective swelling characteristics of polymer brushes were investigated by atomic force microscopy.

An efficient approach to surface-initiated ring-opening metathesis polymerization of cyclooctadiene.

Surface-initiated ring-opening metathesis polymerization of cyclooctadiene (COD), a low ring-strain olefin, is reported for the first time. Polymerization was carried out in the vapor phase, which is advantageous compared to conventional solution methods in terms of minimizing chain transfer by reducing polymer chain mobility at the vapor/solid interface. Attachments of a norbornenyl-containing silane and a Grubbs catalyst to silicon substrates were carried out before samples were exposed to COD vapor. The thickness of grafted 1,4-polybutadiene films was controlled by reaction time and reached approximately 40 nm after 7 h. The polymer films were further chemically modified to afford a new polymer, head-to-head poly(vinyl alcohol).

Fabrication of patterned organic thin film by low-energy electron beam lithography and surface-initiated ring-opening metathesis polymerization

High densities of immobilized polymer brushes have been created on solid supports in a spatially addressable fashion. Octadecyltrichlorosilane was self-assembled on a silicon substrate to form an inert monolayer. The substrate was then patterned by low-energy electron beam lithography. Finally, the exposed region was back-filled with a second functionalized silane and the pattern was further amplified by surface-initiated ring-opening metathesis polymerization. The patterned substrate was imaged by scanning electron microscopy and atomic force microscopy.Key words: patterned thin film, e-beam lithography, ring-opening metathesis polymerization, polymer brushes.

Synthesis of polymer dielectric layers for organic thin film transistors via surface-initiated ring-opening metathesis polymerization.

The use of surface-initiated ring-opening metathesis polymerization (SI-ROMP) for producing polymer dielectric layers is reported. Surface tethering of the catalyst to Au or Si/SiO2 surfaces is accomplished via self-assembled monolayers of thiols or silanes containing reactive olefins. Subsequent SI-ROMP of norbornene can be conducted under mild conditions. Pentacene semiconducting layers and gold drain/source electrodes are deposited over these polymer dielectric films. The resulting field effect transistors display promising device characteristics, demonstrating for the first time that SI-ROMP can be used in the construction of organic thin-film electronic devices.

Surface-Initiated Ring-Opening Metathesis Polymerization on Si/SiO2

Surface-Initiated Ring-Opening Metathesis Polymerization on Si/SiO₂

Patterned polymer growth on silicon surfaces using microcontact printing and surface-initiated polymerization

Patterned polymer films were grown on SiO2/Si surfaces by a process starting with microcontact printing (μCP) of octadecyltrichlorosilane (OTS), formation of a monolayer derived from norbornenyl trichlorosilane (Nbn–SiCl3) in areas not protected by OTS, activation of the surfaces derived from Nbn–SiCl3 with a ruthenium catalyst, and surface-initiated ring-opening metathesis polymerization of derivatives of norbornene by the catalytically active ruthenium species. These patterned polymer films were successfully used as reactive ion etching resists. The combination of μCP and surface-initiated polymerization makes possible molecular-level control of polymer composition and thickness in both lateral and vertical directions: the smallest patterned lateral features were 2 μm lines; this width was determined by the features of the stamp used in μCP and is not the intrinsic limit of the method. The thickness of the polymer film was, typically, 5–100 nm and could be controlled by monomer concentration and reaction time.