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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.
Evolution in the surface modification of textiles: a review
Published in Textile Progress, 2018
Ayoub Nadi, Aicha Boukhriss, Aziz Bentis, Ezzoubeir Jabrane, Said Gmouh
Homopolymerization generally denotes the formation of a linear polymer formed from a monomer or an oligomer, and may be accomplished in many ways, including addition polymerization, step-growth polymerization and ring-opening polymerization. Addition polymerization describes the method where monomers are added one-by-one to an active site on the growing chain. In step-growth polymerization, the molecular weight of the polymer chain builds up slowly and there is only one reaction mechanism for the formation of polymer; ring-opening polymerization is a reaction in which the rings of cyclic monomers are opened, allowing them to be joined together linearly. The polymer types used for affixing these homopolymers to the fibre are diverse, namely polyurethane, polydimethylsiloxane and polyacrylic acid [40].
Ring opening polymerization of lactide: kinetics and modeling
Published in Chemical Engineering Communications, 2019
Sangeeta Metkar, Vivek Sathe, Imran Rahman, Bhaskar Idage, Susheela Idage
The ring opening polymerization (ROP) is usually a preferred polymerization method for large scale production of high molecular weight polymers. However, it is very sensitive to the reactive impurities. To obtain good control over the polymerization rate and MWD of PLA effectively, it is the first priority to remove the potential impurities from all the reagents employed in the ROP (Konstantina et al., 2013; Prokopios et al., 2014). Therefore, the solvents used in the ROP were dried using suitable drying agents and freshly distilled prior to use. The L-lactide ROP was carried out in thick walled corning glass ampoule. The L-lactide was dried by using thermostatic oil bath maintained at 60 ± 0.1 °C under reduced pressure (<1 mmHg) for 4–5 h to ensure the complete removal of moisture. The measured quantity of 1-pyrene butanol and Sn(Oct)2 in toluene was added to the glass ampoule in an inert and moisture-free environment (glove box). The glass ampoule was properly closed and the content was dried further in thermostatic oil bath maintained at 60 ± 0.1 °C for 5–6 h under reduced pressure (<1 mmHg) to ensure the removal of toluene. The glass ampoule was sealed using the standard sealing technique, placed in a programed heating oven and the ROP was carried out at different temperature/time profiles. After prolonged polymerization time the molecular weight starts decreasing and the chain propagation is practically over. Thus, the glass ampoule was quenched in an ice bath for adequate time to achieve high molecular weight polymer. The quenched polymer was isolated after breaking the ampoule and dissolving in dry and freshly distilled chloroform. The unused catalyst was deactivated by adding hydrochloric acid (2N) to the solution. The polymer was separated by precipitation using cold petroleum ether as a non-solvent. The solid white colored precipitated Poly (L-lactide) (PLLA) obtained was separated by filtration. The PLLA obtained was dried in a vacuum oven at 40 °C under reduced pressure (<100 mmHg) for 8–10 h. The unreacted monomer and low molecular weight polymer were separated from the filtrate by removing the solvent on rotary evaporator.