**Author details**

synthesized a group of well-defined s-PP bottlebrush polymers with a molecular weight from 46 kDa to 172 kDa using Grubbs' metathesis catalyst (**Figure 5**) [20]. A decrease in both melting and crystallization temperature was observed and attributed to the constraints on the rigid backbone. Further research by Bates and Hillmyer revealed a scaling transition that depends on the length of the backbone [21]. Hazer evaluated the surface property and mechanical property of a group of graft copolymer containing polypropylene as the backbone and polyethylene glycol (PEG) as the side chain [22]. With 15% of PEG, the graft copolymer demonstrated ultimate stress of 22 MPa and elongation at break of 670%. Bielawski developed a direct C▬H azidation method to introduce azide functionalities into commercially available PP [23] and prepared PP-g-PEG using click chemistry. Tasdelen used a

*Polypropylene - Polymerization and Characterization of Mechanical and Thermal Properties*

"Reactive" polyolefin approach, adding functional monomer units into the polyolefin chain, has emerged as a powerful tool to chemically functionalize poly-

copolymerize α-olefin over styrene [26]. The pendant styrenic vinyl groups in the resulting polymer were quantitatively converted into carboxylic acid groups with thiol-ene addition. The same group further extended this methodology to prepare amino-containing iPP, which exhibited high thermal stability and melting temperature [27]. Chung synthesized a group of hydroxyl-functionalized PP using silaneprotected 10-undecen-1-ol as a comonomer and converted the hydroxyl pendant group into butylated hydroxytoluene (BHT) derivatives (**Figure 6**) [28]. The resulting BHT-functionalized PP demonstrated improved thermal stability and higher dielectric constant. With two methylene group spacers between BHT and ester linkage, the materials displayed superior thermal stability at 190°C compared

Polypropylene is one of the most important plastics in our daily life. However, the materials itself also caused a significant amount of plastic pollution. As much exciting progress has been achieved recently to introduce functionalities and improve both mechanical and thermal stabilities, the research community should also emphasize on developing approaches to recycle PP and PE from the processed

*Synthesis of BHT-functionalized PP (reprinted with permission from Ref. [28]. Copyright 2015 American*

Bu3 catalytic system, which selectively

olefins [25]. Pan copolymerized p-(3-butenyl)styrene and propylene with

similar approach and synthesized PP-g-PCL copolymers [24].

(pyridylamido)Hf/[Ph3C][B(C6F5)4]/Al<sup>i</sup>

with general and capacitor grade PP [29].

product.

**Figure 6.**

**4**

*Chemical Society).*

Weiyu Wang South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou, P.R. China

\*Address all correspondence to: wwang41@vols.utk.edu

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
