Continuous Flow Technology-Enabled Control of Molecular Weight and Distribution for Main-Chain Benzoxazine Precursor BPA-hda and Enhanced Dielectric/Corrosion Resistance of Its Polymer

This study developed a continuous flow process for synthesizing the main-chain benzoxazine precursor BPA-hda, addressing the limitations of traditional batch methods. Under optimal conditions (130 °C, 10 min), the precursor was obtained with a yield of 80.83%, a ring-closed ratio of 95.0%, Mn of 5208 Da, and PDI of 2.24. Compared to batch synthesis, this process reduced reaction time by 96.7% while significantly improving molecular weight and distribution uniformity. Research indicates that under comparable cross-linking density, poly(BPA-hda) derived from narrow distribution (PDI ≈ 2.0) precursors exhibits superior properties: higher hydrophobicity (water contact angle >60°), lower dielectric constant (1.93 at 1 MHz), lower water absorption (<1.7%), and maintained exceptional corrosion resistance in 3.5 wt % NaCl for 60 days. This work achieves precise control of precursor molecular parameters via continuous flow technology and clarifies the structure–property relationship driven by molecular weight distribution.