Semi-interpenetrating polymer network (sIPN) glycol gels offer an exceptional balance between flexibility and mechanical integrity, making them ideal candidates for advanced flexible substrates. We demonstrate a spatially controlled thermal imidization strategy that enables selective mechanical reinforcement within uniform sIPN matrices. Through high-intensity UV irradiation via masking, localized heating drives imidization reaction in designated regions, resulting in enhanced stiffness, tensile strength, and chemical resistance, creating thermally-responsive flexibility gradients across the material. This programmable patterning approach facilitates complex deformation control, targeted reinforcement, and impact chemical resistance. This methodology expands the utility of sIPN Glycol gels for next-generation flexible displays, wearable electronics, and customizable biomedical devices, providing a versatile platform for spatially engineered smart materials.