2: Synthetic Methods in Polymer Chemistry
- Page ID
- 238850
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\)
- 2.1: Ziegler-Natta Polymerization
- There are alkenes that do not give rise to cations stable enough for cationic polymerization, and don't form stable enough anions for anionic polymerization, either. The two most prominent examples are ethene and propene. These monomers are instead polymerized via an organometallic cycle of alkene associations and 1,2-insertions, so that the last alkene becomes part of a metal alkyl group ready to undergo insertion with the next alkene that binds the metal.
- 2.3: Step Growth and Chain Growth
- Step growth and chain growth are two broad classes of polymerization methods. They use monomers with distinct characteristics and display some different growth patterns.
- 2.4: Cationic Polymerization
- Alkenes, or olefins, are probably the most common polymer feedstock. The pi bonds of alkenes are inherently nucleophilic. The addition of an electrophile to an alkene results in cleavage of the pi bond, with the electrons drawn to the electrophile, and consequently a cation can be left on one end of the former double bond.
- 2.5: Living Cationic Polymerization
- Alkenes are a common polymer feedstock, used to make a range of very familiar plastics in everyday use. Because their properties depend strongly on their molecular weights and molecular weight distributions, it is very important to be able to control the growth of these long-chain polymers from their alkene monomers. Termination events contribute to a widening disperity between chains that have undergone these events and those that continue to grow.
- 2.6: Anionic Polymerization
- It seems obvious that cationic methods would be employed for the polymerisation of alkenes. After all, alkenes are nucleophilic, and so they should react readily with cationic initiators. It might be surprising that there are a number of alkene polymerisations that work very well using anionic initiators. One of the most common scenarios for this approach is in the polymerisation of conjugated hydrocarbons, such as styrene
- 2.8: Ring-Opening Polymerization
- On an earlier page, we saw that polyesters and polyamides are typically obtained via condensation polymerization. Ring-opening polymerization (ROP) offers a second approach to these kinds of materials. Using this method, cyclic esters (lactones) or amides (lactams) are opened up to make extended chain structures. The reaction is typically driven by the release of ring strain.
- 2.9: Radical Polymerization
- Radical polymerization is a very common approach to making polymers. There are a number of very reliable methods of carrying out radical polymerization, leading to high molecular weight materials.