Hydrogels with multiple clickable anchor points: synthesis and characterization of poly(furfuryl glycidyl ether)-block-poly(ethylene glycol) macromonomers

Abstract

Functional polyacrylamide hydrogels containing multiple furfuryl anchor points for Diels–Alder reactions were prepared employing new macromonomers. For this purpose, α-diphenylmethyl-ω-4-vinyl benzyl-poly(furfuryl glycidyl ether)-block-poly(ethylene glycol) (PFGE_p-b-PEG_q) macromonomers were synthesized via anionic ring opening polymerization in four different block lengths: PFGE₁₀-b-PEG₂₅, PFGE₈-b-PEG₇₉, PFGE₁₈-b-PEG₆₆ and PFGE₁₃-b-PEG₁₁₁. These furan containing building blocks were characterized by ¹H NMR, ¹³C NMR and FT-IR spectroscopy, size exclusion chromatography and MALDI TOF mass spectrometry and revealed low molar mass dispersities between 1.05 and 1.09 and number average molar masses between 2330 g mol⁻¹ and 6660 g mol⁻¹. The block lengths of the macromonomers were adjustable via the monomer-to-initiator ratio and high end group functionalization degrees between 72% and 98% were achieved. The macromonomers were characterized by DSC and TGA regarding their thermal properties (−43 °C ≤ T_g ≤ −32°, 32 °C ≤ T_m ≤ 45 °C, 369 °C ≤ T_d ≤ 381 °C) and by tensiometry regarding their surface activity, revealing a critical micelle concentration around 0.3 mg mL⁻¹ in aqueous solution. The furfuryl groups of the PFGE_p-b-PEG_q macromonomers were reactive in Diels–Alder reactions in solution as well after their integration into polyacrylamide hydrogels by radical copolymerization, as shown by fluorescence labeling employing a maleimide-functionalized dye. Thus, a new synthetic route is opened up to access functional hydrogels providing clickable anchor points in high density for conjugation of maleimide-functional substrates.