Isotactic polypropylene is a rigid (i

Subject:ChemistryPrice: Bought3

Share With

Isotactic polypropylene is a rigid (i.e. high modulus) plastic that is inexpensive and energy efficient to produce. However, the impact properties of iPP homopolymer are very poor and make it unsuitable for many automotive applications. To address this, impact-modified iPP is produced, which is a copolymer of iPP with a small amount of ethylene comonomer. 

1. What is the primary molecular/physical property affected by incorporating only a small amount of ethylene comonomer which improves its impact strength? 

2. Using iBu3Al/TiCl4 as a catalyst package produces the following structure.  

3. What is the insertion regiochemistry? 

4. What is the pathway of termination? 

5. If heterogeneous Ziegler-Natta catalysts are used to produce impact modified iPP (i.e. ethylene-co-propylene), a significant amount of undesired chains form. For example, low molecular weight chains with no crystallinity, the ethylene comonomer is not evenly distributed within the chains, and some chains contain no ethylene at all. Propose/draw a homogeneous catalyst package (catalyst and co-catalyst) that can overcome the above limitations.