Here's the list of the polymers you've mentioned in order of increasing melting temperature:

1. LDPE (Low-Density Polyethylene): ~110°C to 120°C

2. HDPE (High-Density Polyethylene): ~130°C to 135°C

3. PMMA (Polymethyl Methacrylate): ~160°C to 200°C

Explanation:

* Polyethylene (PE): The density of polyethylene (PE) is directly related to its melting point. LDPE has a lower density because its molecules are more branched, leading to weaker intermolecular forces and a lower melting point. HDPE has fewer branches, resulting in stronger intermolecular forces and a higher melting point.

* Polymethyl Methacrylate (PMMA): PMMA is a more rigid polymer than polyethylene. It has a more complex molecular structure with strong dipole-dipole interactions, leading to a significantly higher melting point.

Let me know if you have any other questions about polymers!