Binding of Functionalized Polymers to Surface-Attached Polymer Networks Containing Reactive Groups

Abstract

To study diffusion and binding of polymers into surface-attached networks containing reactive groups, surface-attached polymer networks bound to oxidized silicon surfaces are generated, which contain succinimide ester groups. The surface-attached polymer layers are brought into contact with poly(ethylene glycol)s (PEG), which carry terminal amine end groups and which have systematically varied molecular weights. The coupling reaction between the active ester groups in the polymer networks and the amine groups in the incoming chains are studied by ellipsometry, surface plasmon spectroscopy, AFM, and Fourier transform infrared spectroscopy (FTIR). The degree of functionalization of the reactive layers by the PEG-NH 2 depends strongly on the crosslink density of the network, the active ester content, and the molecular weight of the amine-terminated polymer. A model for the attachment reaction is proposed which suggests that the incoming polymer chains bind only at the outer periphery of the network in a narrow penetration zone. According to this model, when the incoming polymers are rather short, penetration into the layer and binding are prohibited by the high segment density and the anisotropic stretching of the surface-attached networks ("entropic shielding"). For incoming chains with a higher molecular weight and/or networks with a small mesh sizes, size exclusion effects determine diffusion and binding.

Adhesion Behavior of Ti–PMMA–Ti Sandwiches for Biomedical Applications

“…this was the temperature limit used for all the cases. While a higher density of the grafted polymer caused problems in getting stronger adhesion in other studies, [13][14][15] this was not observed in the current one. A possible reason could be the longer processing time used for the process.…”

“…In previous studies, it was found that highly dense grafted polymers result in decreased adhesion, as it leads to overlapping of grafted chains, thus preventing interpenetration. [13][14][15] Thus, the grafted chain density should be in a regime where they can easily move and interpenetrate in the adhering polymer. As polymer autohesion is also a timedependent process, by increasing the processing time, the degree of bonding between the polymers will also increase.…”

On the Lubrication Mechanism of Surfaces Covered with Surface‐Attached Hydrogels

“…To this first a copolymer containing photoactive benzophenon groups (PDMAA‐ co ‐MABP) is generated from N , N ′‐dimethylacrylamide (DMAA) and 4‐methacryloyloxybenzophenone (MABP). The synthesis of the polymers and the photocrosslinking for the generation of surface‐attached networks from these layers has been described in detail in previous publications . Briefly, upon irradiation of the dry, glassy polymer film with UV light the benzophenone units are excited into a biradicaloid triplet state, abstract a hydrogen from any alkyl moiety in the vicinity such as a neighboring polymer chain, followed by radical–radical coupling leading to a covalent linking of the chains (C,H insertion crosslinking, Chic).…”

“…It should be noted that due to the stretching and the block‐like segment density profile exhibited by swollen surface‐attached networks such systems are strongly impermeable by other macromolecules, which strongly prevents any interpenetration by other chains coming in from the outside. This effect was found to be even more pronounced than that of polymer brushes as penetration occurs only at the outer periphery of the layers and surface‐attached networks can have an even steeper segment density profile compared to brushes . As the essential physics of surface‐attached gels is very different from that of free gels also the friction properties should be very different.…”

Multivalent Noncovalent Interfacing and Cross‐Linking of Supramolecular Tubes

“…[ 10,11 ] Numerous strategies have been developed for controlled interfacing of these polymer networks with solid substrates via specific interactions including on‐surface growth of polymer networks. [ 12,13 ] These avenues have been explored in supramolecular polymer systems to much lesser extent, primarily relying on poorly controlled and nonspecific interactions between supramolecular fibers. [ 14 ] Recently reported chemically cross‐linked supramolecular fibers yielding strain‐stiffening, self‐healing hydrogels demonstrate their potential as dynamic new materials.…”