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Monomers and Polymerization Methods

Several monomers are used for polymers. Most of them are old but some of them are fresh materials. Here, monomer types and monomers are given and also special methods for polymerization.

A lot of these materials are collected in books (1-6).

Monomers can be subdivided into two classes, depending on the kind of polymer that they form (7). Monomers that participate in condensation polymerization have a different stoichiometry than monomers that participate in addition polymerization. Classifications may also include (8):

1. Alkylene monomers
2. Epoxide monomers
3. Diols
4. Diacids
5. Amino acids
6. Alcohol acids
7. Bio-based monomers
8. Nucleotides
9. Monosaccharides
10. Natural monomers
11. Synthetic monomers
12. Polar monomers
13. Nonpolar monomers

1.1 Types of Monomers and Synthesis Methods

In this section, common monomers, both conventional and modern monomers, are shown.

1.1.1 Alkylene Monomers

Various monomer types are presented in Tables 1.1, 1.2, and 1.7 below. Also, these compounds are shown in Figures 1.1 and 1.2.

Table 1.1 Monomers with one double bond.

Table 1.2 Monomers with multiple double bonds.

Some modern alkene-based monomers are shown in Table 1.3.

1.1.1.1 Apopinene

Apopinene (6,6-Dimethylbicyclo[3.1.1]hept-2-ene), c.f. Figure 1.4, is a biorenewable monomer that can be used for ring-opening metathesis polymerization (9).

Figure 1.1 Monomers with one double bond.

Table 1.3 Modern Monomers.

Figure 1.2 Monomers with multiple double bonds.

Figure 1.3 Cyclic monomers with multiple double bonds.

Figure 1.4 Apopinene.

Apopinene is the most abundant monoterpene present in nature and plays a crucial role in many biological, atmospheric and industrial processes. Similar to many other readily accessed and biorenewable terpenes, a-pinene is widely used in both the fine chemical and polymer industries. The Lewis acid-catalyzed polymerization of a-pinene generates a polymer and has found a variety of uses in a plethora of industrial applications such as adhesives, plastics, and rubbers.

The high abundance, low cost, and biorenewability of a-pinene make its incorporation into additional novel materials highly desirable from the standpoint of sustainability.

One avenue that has sparked some theoretical interest is the ring-opening metathesis polymerization of a-pinene (11).

1.1.2 Epoxide Monomers

Various epoxide monomers are presented in Table 1.4. Some of these monomers are also shown in Figure 1.5.

The synthesis of functionalized polycarbonates, employing mainly propylene oxide and cyclohexene oxide, has been detailed (12). In recent years, functionalized polycarbonates have become an emerging topic with a broad scope of potential applications. The synthetic routes and properties of numerous functionalized polycarbonates synthesized from CO2 and functional epoxide monomers have been described (12).

The synthesis of polymers from renewable resources is of high interest. Polymeric epoxide networks constitute a major class of thermosetting polymers and are extensively used as coatings, electronic materials, and adhesives (13). Owing to their outstanding mechanical and electrical properties, chemical resistance, adhesion, and minimal shrinkage after curing, they are used in structural applications as well.

Most of these thermoset types are industrially manufactured from bisphenol A (BPA), a substance that was initially synthesized as a chemical estrogen (13). The awareness of BPA toxicity combined with the limited availability and volatile cost of fossil resources and the non-recyclability of thermosets implies necessary changes in the field of epoxy networks. Thus, substitution of BPA has witnessed an increasing number of studies both from the academic and industrial sides. This review presents an overview of the reported aromatic multifunctional epoxide building blocks synthesized from biomass or from molecules that could be obtained from transformed biomass.

Table 1.4 Epoxide Monomers.

Figure 1.5 Epoxide monomers.

The main glycidylation routes and mechanisms and the BPA toxicity were described. Also, the main natural sources of aromatic molecules have been detailed. The various epoxy prepolymers can be organized into simple mono-aromatic di-epoxy, mono-aromatic poly-epoxy, and derivatives with numerous aromatic rings and epoxy groups (13).

1.1.3 Diol-Based Monomers

Diol-based monomers are presented in Table 1.5 and shown in Figure 1.6.

Table 1.5 Diol based monomers.

Figure 1.6 Diol-based monomers.

The synthesis and characterization of variants of poly(diol fumarate) and poly(diol fumarate-co-succinate) were described. Through a Fischer esterification, a, ?-diols and dicarboxylic acids were polymerized to form aliphatic polyester comacromers. Because of the carbon-carbon double bond of fumaric acid, incorporating it into the macromer backbone structure resulted in unsaturated chains.

By choosing a, ?-diols of different lengths (1,6-hexanediol, 1,8-octanediol, and 1,10-decanediol) and controlling the amount of fumaric acid in the dicarboxylic acid monomer feed (33, 50, and 100 mol%), nine diol-based macromer variants were synthesized and characterized for molecular weight, number of unsaturated bonds per...