University:
Massachusetts Institute of Technology
Course:
3.091SC | Introduction to Solid State Chemistry
Academic year:

2020
Views:

234

Pages:

2
Author:

Eden Robbins

Session #28: Homework Solutions Problem #1 Poly (vinyl chloride) is represented by the formula Draw molecular structures for tetramers (n=4) of the atactic, isotactic, and syndiotactic forms of PVC. Solution (a) atactic: isotactic: syndiotactic: Problem #2 (a) Polyethylene exists either as a linear (straight-chain) polymer or as a branched polymer. Which is the high-density form? Explain. (b) In visible light high-density polyethylene (HDPE) is opaque (white) while lowdensity polyethylene (LDPE) is transparent. Explain. (c) Which form of PE is mechanically more flexible? Explain. (d) Which form of PE has the higher melting point? Solution a) – linear is HDPE – straight chains pack better (b) HDPE straight chains are capable of some degree of crystallization ⇒ interface between amorphous and crystalline material scatters visible light ⇒ white appearance. (c) semi-crystalline nature of HDPE adds rigidity ⇒ LDPE is more flexible (d) partial crystallization leads to better packing which in turn implies a higher degree of secondary bonding within the macromolecule ⇒ HDPE has the higher melting point

Session #28: Homework Solutions

of 2

Description

Free up your schedule!

Take 5 seconds to unlock