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Biodegradable Polymers
Published in Ram K. Gupta, Conducting Polymers, 2022
Eman Abdallah Ismail, Mbuso Faya, Edith Amuhaya, Calvin A. Omolo, Thirumala Govender
Ring-opening polymerization (ROP) is a class of polymerization whereby a cyclic monomer is utilized to produce a polymer that lacks cyclic structures in its backbone [18, 22]. It is associated with higher molecular weight polymers compared to polycondensation. However, a major drawback is the costly manufacturing of the cyclic oligomers at the industrial level [24]. It is a type of chain-growth polymerization in which the end of the polymer chain acts as a reactive site and is used to form a longer polymer chain by ring-opening of the cyclic monomers. Depending on the types of groups on the monomer, three types of reactive sites can be generated in ROP: anionic, cationic, or radical. This makes ROP a highly versatile method for synthesizing polymers. ROP proceeds with the use of metal or metal-ligand catalysts, using metals such as Li [25], Fe [26], Mg [27], and Zn [28], among others being used to successfully prepare a variety of polymers. ε-Caprolactone, d-valerolactone, and lactic acid are among the commonly used monomers [29].
Molecular Description of Heterophase Polymerization
Published in Hugo Hernandez, Klaus Tauer, Heterophase Polymerization, 2021
Ring-opening polymerization is a particular case of chain-growth polymerization where an active site breaks a bond in a cyclic monomer and incorporates the resulting acyclic structure into the backbone of the polymer. In the case of supramolecular polymerization, a ring-chain polymerization mechanism is possible, but the ring opening takes place by physical forces rather than by an active chemical site.
Shrinkage in Conventional Monomers During Polymerization
Published in Rajender K. Sadhir, Russell M. Luck, Expanding Monomers, 2020
Russell M. Luck, Rajender K. Sadhir
The molecular weight of the growing polymer during chain-growth polymerization increases very rapidly even though the conversion of the monomer to polymer is low. Upon termination, the polymer usually consists of a mixture of an extremely high molecular weight polymer and a small amount of unreacted monomer.
Revisiting the Early History of Synthetic Polymers: Critiques and New Insights
Published in Ambix, 2018
All of the synthetic polymers hitherto well treated in the early period of macromolecules (such as polystyrene, polyisoprene, and poly(vinyl chloride)) are examples of materials now known as “addition” polymers, one of two general polymer class designations introduced by the DuPont chemist Wallace Carothers (1896–1937) in 1929.82 Polymers in this class are produced by various forms of addition polymerisation,83 in which monomers are converted to the corresponding polymer without the generation of a secondary by-product. Mechanistically, the majority of addition polymers are generated via “chain-growth” polymerisation, in which the polymer chain grows by the addition of sequential monomers to the active end of the polymer chain.