I found an excellent price for a flight to Chicago by Turkish airlines. My only concern is that the layover time is only 1hr 30min. Is this time sufficient to catch the next flight?
According Turkish Airlines's transfer passenger procedures, for all passengers transferring between international flights, there is no passport procedure. This is consistent with the fact that nobody needs a transit visa for Turkey.
If the connecting flights are both on Turkish Airlines, a codeshare or an allied (Star Alliance) airline, then you'll have been given a boarding pass for the whole journey at your point of departure. If the flights are on different airlines, you may need to get a boarding pass for the second leg, but usually you can print your boarding pass at home before departure, and even if you can't, there is rarely a long queue at transfer desks.
If your flights are on a single ticket, your luggage is automatically transferred between the flights. If they're on separate tickets, you'll need to reclaim your hold luggage and check it in again for the second flight. That's amply doable in 1½ hours provided your first flight is on time.
In conclusion, if your flights are on a single ticket, 1½ hour is plenty of time for a transfer. If your flights are on separate tickets, on the other hand, it's a huge risk. The problem is not the time it takes to re-check your hold luggage, but the risk of missing your connection if the first flight is late. With a single ticket, the airline will re-book you and pay for hotels and meals if necessary (though not pay for any loss of revenue due to e.g. missing a critical business meeting).
Generally speaking, if an airline is willing to sell you two flights on the same ticket, they're taking the responsibility of ensuring that you don't miss your connection, and will endeavor to find a solution if one flight is late. With a single ticket, the one thing you do need to check is whether you need to go through passport controls, because the expected time for that can sometimes vary a lot depending on your nationality. This is especially the case when arriving in the US where the queue at some of the biggest airports can be very slow for people with a visa, but very fast for a US citizen. Since Turkey doesn't do passport checks for passengers in transit, this is not an issue in your case.
Yes, if you're traveling on the same ticket, 1:30h is enough for you not to worry about the connection. You may still miss the next flight if the first leg arrives very late, but Turkish Airlines will do everything in their power to deliver you to your final destination and compensate generously for any inconvenience. In case you're traveling on two different tickets, you should reserve much longer time for the transfer.