Chemical synthesis, polymers growth conditions

Conditions that are important to all chemical reactions such as stoichiometry and reactant purity become critical in polymer synthesis. In step growth polymerization, a 2% measuring and/or impurity error cuts the degree of polymerization or the molecular weight in half. In chain growth polymerization, the presence of a small amount of impurity that can react with the growing chain can kill the polymerization. 

Although the first publications concerned with the possibilities of use of microwave irradiation in organic synthesis appeared in 1980 s [12,13] and in polymer chemistry even earlier at the end of 1960 s [14], the sudden growth of interest in the application of microwave irradiation in almost all fields of chemistry took place at the end of 1980 s. Nowadays, there is hardly find any reaction that has not been attempted under microwave conditions. The application of microwaves in chemistry is therefore so attractive that from the very beginning it was realized that a number of chemical processes can be carried out with a substantial reduction in the reaction time in comparison to conventional processes. Reactions that usually take many hours or days, under influence of microwave irradiation can be run in considerably shorter time of several minutes or even seconds [15]. These phenomena are not fully understood yet however, there are two groups of theories that are proposed to explain the reduction of the reaction time under microwave conditions in comparison with processes under conventional conditions. 

Electrochemical polymerisation produces films on an electrode surface.. Under controlled conditions uniform films up to a few mm thick, which carl be removed from the electrode for subsequent study, can be prepared. Physical properties can be modified by choice of the counterions (dopants) included in the film during growth. It is, however, more difficult to control chain structure and crosslinking than in chemical methods. Electrochemically produced polymers are, therefore, less well characterised than the best directly-synthesised polymers. While this is less satisfactory for fundamental investigations, it is of less concern for applications such as battery electrodes, artificial muscles and drug release agents. The two main approaches, direct-synthesis and electrochemical, are described in the following two sections. 

Whereas 2,5-dihydroxymethylfuran (DHMF) has been proposed frequently as a diol component for polyester synthesis, the high reactivity of the hydroxymethyl groups under acidic conditions primarily leads to resin formation, which is commercially exploited for the production of thermoset furan resins [55]. Although HMFA is more chemically stable than DHMF, it is also prone to resinification at high temperatures. In contrast, FDCA and derivatives have proven to be chemically stable under conditions relevant to polyester synthesis, making them the most versatile and industrially viable furan monomers for step growth polymers. 

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