Mix mustard, brown sugar, apple juice, and Worcestershire sauce together in a bowl until marinade is smooth. Pour 2/3 the marinade into a large resealable plastic bag. Add pork chops, coat with marinade, squeeze out excess air, and seal the bag. Marinate in the refrigerator for 8 hours to overnight. Cover bowl with remaining marinade with plastic wrap and refrigerate.
Remove pork chops from marinade and discard bag and marinade.
Preheat grill for medium heat and lightly oil the grate.
Cook the pork chops on the preheated grill, basting with reserved marinade, until no longer pink in the center, 4 to 5 minutes per side. An instant-read thermometer inserted into the center should read 145 degrees F (63 degrees C). Let pork chops stand for 5 minutes before serving.