Ring Opening Metathesis Polymerization Review

Ring Opening Metathesis Polymerization Review-55
Liquid crystalline polymers (LCPs) have gained attention as materials with interesting optical, mechanical and rheological properties.

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Ring-opening of cyclic monomers is often driven by the relief of bond-angle strain.

Thus, as is the case for other types of polymerization, the enthalpy change in ring-opening is negative.

The mesophase type and the thermal transition temperatures are influenced not only by the attached mesogenic moiety but also by the stiffness of the polymer backbone, the spacer lengths between the main chain and the liquid crystalline entity, the isomerism, the tacticity, and so on.

In addition, the use of acyclic diene metathesis polymerization (ADMET) or alternating diene metathesis polycondensation (ALTMET) offer new possibilities for creating new main chain liquid crystalline polymers (MCLCPs).

Modified from the earlier definition In polymer chemistry, ring-opening polymerization (ROP) is a form of chain-growth polymerization, in which the terminus of a polymer chain attacks cyclic monomers to form a longer polymer (see figure).

Ring Opening Metathesis Polymerization Review 4 Problem Solving Steps

The reactive center can be radical, anionic or cationic.Synthesis of polypeptides which has the oldest history of ROP, dates back to the work in 1906 by Leuchs.Subsequently, the ROP of anhydro sugars provided polysaccharides, including synthetic dextran, xanthan gum, welan gum, gellan gum, diutan gum, and pullulan.Following Flory–Huggins solution theory that the reactivity of an active center, located at a macromolecule of a sufficiently long macromolecular chain, does not depend on its degree of polymerization (DPi), and taking in to account that ΔG, for polymerization in the bulk, are well above or below the operable polymerization temperatures, respectively.The polymerization of a majority of monomers is accompanied by an entropy decrease, due mostly to the loss in the translational degrees of freedom.Examples of cyclic monomers that polymerize through this mechanism include lactones, lactams, amines, and ethers.The mechanism is affected by the stability of the resulting cationic species.Many strained cycloalkenes, e.g norbornene, are suitable monomers via ring-opening metathesis polymerization.Ring-opening polymerization has been used since the beginning of the 1900s to produce polymers.Monomers with a three-member ring structure - such as epoxide, aziridine, and episulfide - undergo anionic ROP.Cationic initiators and intermediates characterize cationic ring-opening polymerization (CROP).

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