# How can I explain PEO-b-PLA behaviors in dissolution?

I dissolved PEO 10K - PLLA 14K in toluene at the concentration of $$\pu{50 mg/ml}$$, $$\pu{25 mg/ml}$$, and $$\pu{5 mg/ml}$$ including $$\pu{30 min}$$ of sonication.

When I sonicated them at room temperature, only $$\pu{5 mg/ml}$$ was clear solution but others were cloudy.

However, when I did at $$\pu{50 ^\circ C}$$, all the solutions were clear initially, but only $$\pu{50 mg/ml}$$ solution became cloudy as it naturally cooled to room temperature.

I measured and compared water/solution interfacial tensions, and I found that solutions sonicated at room temperature showed relatively higher surface tension than those sonicated at $$\pu{50 ^\circ C}$$. I think this means some of polymers are not dissolved or highly aggregated so that they did not effectively act as surfactants.

My questions are:

1. What does clear/unclear solution mean? Is it not dissolved? Or is it highly aggregated?
2. Solutions of $$\pu{25 mg/ml}$$ and $$\pu{5 mg/ml}$$ were clear in both cases but have different interfacial tension. How can I explain this?