ROMP is a chain-growth polymerization process in which a cyclic olefin is converted to a polymeric material. The mechanism of the polymerization, proposed by Y. Chauvin, is based on olefin metathesis and involves a unique metal-mediated carbon—carbon double-bond exchange process, leading to an unsaturated polymer. Initiation begins with the coordination of a cyclic olefin to a transition-metal alkylidene complex, forming a four-membered metallacyclobutane intermediate that breaks up productively to generate a new metal alkylidene propagating alkylidene.
Analogous steps are repeated during the propagation stage until polymerization ceases that is, all the monomer is consumed or the reaction is terminated.
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- Ring Opening Metathesis Polymerisation and Related Chemistry.
The use of well-defined initiators combines rapid initiation with high propagation rates and often enables living polymerizations that is, reactions for which there is no termination step to stop chain growth. Thus, precise adjustment of the molecular weight can be accomplished by simply varying the ratio of monomer to initiator. The living character of ROMP enables the synthesis of well-defined, end-functionalized polymers as well as block and graft copolymers with complex architectures and useful functions.
These BCPs spontaneously assemble into a spherical micelle in aqueous environments. Drug release can be manipulated by choosing biodegradable polymers with different surface or bulk erosion rates, and external conditions such as pH and temperature changes may function as a switch to trigger drug release . Alternatively, NSBBs can be formed by growing chains from the single NP surface after anchoring a suitable catalyst on it, which will be more precise, however, much less effective.
Pure and Applied Chemistry
This has not been achieved synthetically in a precisely controlled manner, yet. Within the past decades, the sol—gel process has been widely used in the bottom-up fabricating of novel organic—inorganic hybrid materials. In the case of composites, the goal is to carry out the sol—gel reaction in the presence of polymeric molecules and contain functional groups to improve their bonding to the inorganic phase .
This is a very useful novel reinforcement technique, which can generate reinforcing NPs within a polymer matrix. The sol—gel process surpasses the traditional blending method since it can subtly control the morphology or surface characteristics of the growing inorganic phase in the polymer matrix by control of these reaction parameters.
Choice of base or acid catalyst controls both the process kinetics and the size of the resulting inorganic inclusions. Goodall, in Encyclopedia of Materials: Science and Technology , These polymers are based on a two-step process ring-opening metathesis polymerization ROMP , followed by hydrogenation.
ring-opening metathesis polymerization - an overview | ScienceDirect Topics
The polymers, made using two component homogeneous catalysts typically MoCl 5 in combination with an alkylaluminum halide , are hydrogenated employing palladium catalysts. The resulting polymers show excellent transparency and find a number of applications, taking advantage of their optical properties e. McInnes, N. Voelcker, in Porous Silicon for Biomedical Applications , One of the earliest examples of surface-initiated polymerization from PSi was demonstrated by Yoon et al.
This process generated a composite material that was chemically and mechanically very stable. Errien et al. Both methods of polymerization gave a homogeneous polymer layer. Pike et al. Xia et al. Stringent washing assured that physisorbed polymer chains were removed from the surface Xia et al. In , Gorman et al. The resulting composites have been studied to determine the effect the porosity exerted on the molecular weight and polydispersity during surface-initiated polymerization.
This was attributed to the increase of confinement of the growing polymer chains. In , Chiboub et al. The oxidized PSi surface was reacted with 3-bromopropyltrichlorosilane to yield a brominated surface. They then performed the graft polymerization of aniline to the surface using either oxidative polymerization or electrochemical polymerization using cyclic voltammetry.
These composites have potential applications in sensing devices. Both PSi and PLLA show good biocompatibility and tunable degradation behaviour, suggesting composites of these materials to be suitable to support localized drug delivery into the human body. Composite materials were loaded with a model cytotoxic drug, camptothecin CPT.
Release profiles of CPT showed distinct characteristics for each of the composites studied. The limited linear phase release exhibited by PSi-PLLA composites was adequate for short-term release application, such as that required for the delivery of antibiotics, but clearly unsuitable to support long-term controlled drug release. The cytotoxicity of the composites was confirmed by contact with human lens epithelial SRA cells.
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Monolithic materials were determined to induce maximum cell death over the 5 day monitoring period. We believe that biodegradable hybrid materials such as these will find use in tissue engineering and drug delivery, for example in applications where complex degradation profiles are required that cannot be achieved with one type of material alone.
Ring-opening Metathesis Polymerization
About this page. Learn more about ring-opening metathesis polymerization. Ring Opening Metathesis Polymerization M. Piotti, in Encyclopedia of Materials: Science and Technology , ROMP technology allows the preparation of specialty polymers that are not accessible by other polymerization methods. Self-Healing of Different Polymers George Wypych, in Self-Healing Materials , Self-healing system based on ring opening metathesis polymerization and an amine-epoxy reaction contain multiwalled tri-axial fibers see Figure Amass, in Comprehensive Polymer Science and Supplements , 6.
Self-healing composites M. First successful demonstration of self-healing in a thermosetting polymer. White et al. Further refinement of material system to investigate the influence of healing time, catalyst and microcapsule loading, catalyst form, and damage mode. Brown et al.
Kessler et al. Self-healing demonstrated in a system where the healing agent is dispersed via phase separation. Ref country code : BE. Ref country code : CZ. Ref country code : SK. Ref country code : RO. Ref country code : EE.
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Ref legal event code : PCAR. Ref legal event code : PL. Ref legal event code : ST. Ref country code : LI. Dental material being polymerizable by ring-opening metathesis polymerization comprising i at lest one ruthenium complex bearing at least one N-heterocyclic carbene ligand or precursors which generate a ruthenium complex bearing at least one N-heterocyclic carbene ligand in situ; and ii at least one cyclic olefin capable of metathesis. This invention relates to polymerizable compositions which can be polymerized by visible-light-induced ring-opening metathesis polymerization.
These compositions are particularly useful as dental materials for operative and prosthetic dentistry.