Acute Degradation of Surface-Bound Unsaturated Polyolefins in Common Solvents under Ambient Conditions

Abstract

We describe the detachment of covalently grafted polybutadiene and polynorbornenechains -which were prepared by surface-initiated ring-opening metathesis polymerization (SiROMP) -from Si/ SiO 2 substrates upon brief exposure to common solvents in air. Degradation and disappearance of grafted polybutadiene films after successive rinses with dichloromethane was monitored by ellipsometry. Changes in surface topography were analyzed by atomic force microscopy. The rapid auto-oxidation of allylic carbon-hydrogen bonds renders these thin films extremely susceptible to degradation under ambient conditions. Polymers in the tethered state suffer more acute degradation (on the time scale of seconds) compared to those dissolved in solution (not detectable after days). To prevent degradation, unsaturated polymersprepared by SiROMP and the subsequent conversion (of unsaturated groups) need to be carriedout under inert atmosphere. For example, smooth polybutadiene thin films of ~ 100 Å thick were covalently attached to silicon substrates via SiROMP of cyclooctadiene in the vapor phase. Solvent rinsing to remove unreacted monomers and free oligomers/polymers was carried out prior to the conversion of double bonds to epoxide groups. When these steps were carried out under nitrogen, negligible film loss was observed and surface topography of the thin film was preserved. Once the unsaturation was removed from polybutadiene, the epoxidized and hydroxylated polybutadiene films were stable toward solvent exposure in air.

Internal plasticization of poly(vinyl) chloride using glutamic acid as a branched linker to incorporate four plasticizers per anchor point

“…However, sulfide linkers are susceptible to oxidation, leading to both discoloration and degradation over time. The disadvantage of using amine nucleophiles to displace chloride on PVC is that amines are also excellent bases, leading to inevitable competitive elimination, resulting in unsaturation in the polymer chain and consequent low thermal stability . Another method to attach plasticizers to PVC is copper‐catalyzed azide‐alkyne cycloaddtion .…”

“…The disadvantage of using amine nucleophiles to displace chloride on PVC is that amines are also excellent bases, leading to inevitable competitive elimination, resulting in unsaturation in the polymer chain and consequent low thermal stability. 29 Another method to attach plasticizers to PVC is coppercatalyzed azide-alkyne cycloaddtion. [30][31][32][33][34][35][36][37][38] However, the use of a copper catalyst leaves a toxic copper residue.…”

Molecular Mechanochemistry: Engineering and Implications of Inherently Strained Architectures

“…A later study by Chen et al reported that surface-grafted polybutadiene (PBd) and polynorbornene (PNb) brushes suffered acute degradation upon solvent rinsing under ambient conditions, leading to the decrease in film thickness [152]. The degradation was ascribed to the rapid auto-oxidation of allylic carbon-hydrogen bonds, supported by an earlier work by Jennings and co-workers which demonstrated that the loss of PNb films was probably caused by the cleavage of polymer chains at the olefin sites [153] and the control experiment that degradation of PBd film did not occur when solvent rinsing was carried under nitrogen in a glovebox.…”

Surface-Initiated Ring-Opening Metathesis Polymerization in the Vapor Phase: An Efficient Method for Grafting Cyclic Olefins with Low Strain Energies

“…24,25 We showed that carrying out SiROMP of COD in the vapor phase is a viable approach in grafting polybutadiene (PBd) on Si/SiO 2 substrates, yielding ~ 10 nm thick films after 30 min of polymerization time at room temperature. Commonly, ROMP of low-strain cyclic olefins is complicated by competing chain transfer reactions.…”