Final answer:
The differences in glass transition temperature for but-1-ene and poly(but-2-ene) are due to the position of the double bond, affecting chain flexibility. For ethyl acrylate and poly(methyl methacrylate), the presence of a methyl group in PMMA increases steric hindrance and thus the Tg.
Step-by-step explanation:
The glass transition temperature (Tg) of a polymer reflects the temperature at which it transitions from a hard, glassy material to a soft, rubbery one. This temperature is influenced by the polymer's molecular structure, including factors like the size and shape of its monomer units, the flexibility of its polymer chains, and the presence of any bulky side groups or cross-linkages.
For but-1-ene and poly(but-2-ene), the difference in Tg can be attributed to the placement of the double bond within the polymer chain. But-1-ene has the double bond at the end of the chain, leading to a higher Tg as this configuration allows for more intermolecular interactions and less flexibility compared to poly(but-2-ene), which has the double bond in a more central position.
The difference in Tg between ethyl acrylate and poly(methyl methacrylate) (PMMA) can be explained by the presence of a methyl group attached to the carbon atom of the backbone chain in PMMA. This methyl group adds steric hindrance, reducing the overall flexibility of the polymer chain and resulting in a higher glass transition temperature compared to ethyl acrylate, which lacks this substituent.