What does it mean for a higher glass transition temperature in terms of crystallinity? The glass transition temperature is associated with amorphous regions in a polymer. If I have observed in a lab experiment that polymers with a higher glass transition temperature tend to have less crystalline structures, how should I interpret this?
A higher glass transition indicates less energy is required for the bonds of the glass to relax their strain. This is usually due to a slower cooling rate. In a slower cooling rate regime, more time is allowed for crystallization to occur.  So while you are correct to observe a correlation, one does not cause the other but rather they have a common cause of the slower cooling rate.