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    Polyglycolic acid from the direct polymerization of renewable C1 feedstocks
    (Royal Soc Chemistry, 2015) Gokturk, Ersen; Pemba, Alexander G.; Miller, Stephen A.
    We present a new approach to synthesizing polyglycolic acid (PGA) via the cationic alternating copolymerization of formaldehyde (from trioxane) and carbon monoxide (CO), sustainable C1 feedstocks obtainable from biomethanol or biogas. This method constitutes an inexpensive and efficient pathway for the synthesis of PGA, circumventing the usual route requiring glycolide. PGA was successfully synthesized with yields up to 92% from trioxane, 800 psi of CO, and 1 mol% triflic acid (TfOH) initiator at 170 degrees C over three days. H-1 NMR, C-13 NMR, and FT-IR spectra of the polymer from CO and trioxane are identical to those of commercial PGA prepared via the ring-opening polymerization of glycolide-confirming the alternating microstructure. Although high copolymerization conversions were obtained, molecular weight analysis usually suggested the formation of oligomeric glycolic acid (OGA). High molecular weight PGA can be obtained via post-polymerization polycondensation of OGA catalyzed by Zn(OAc)(2)center dot 2H(2)O. Alternatively, increased molecular weight PGA can be achieved by inclusion of glycerol as a branching agent during the C1 copolymerization.
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    Silicon Acetal Metathesis Polymerization
    (Amer Chemical Soc, 2016) Sahmetlioglu, Ertugrul; Ha Thi Hoang Nguyen; Nsengiyumva, Olivier; Gokturk, Ersen; Miller, Stephen A.
    A kinetic study revealed that the acid-catalyzed (p-TSA) equilibration of Me2Si(OMe)(2) and Me2Si(OEt)(2), forming Me2Si(OEt)OMe, is established in 300 min in benzene at room temperature. This silicon acetal metathesis reaction is exploited for the step-growth polymerization of bissilicon acetals (MeOSiMe2OROSiMe2OMe) with metathetical loss of Me2Si(OMe)(2). Thus, a convenient and generalized silicon acetal metathesis polymerization (SAMP) method is introduced as the acid-catalyzed copolymerization of a diol (HOROH) and Me2Si(OMe)(2), driven by elimination of methanol and/or Me2Si(OMe)(2). SAMP constitutes an effective and powerful strategy for manipulating the most common bond in the Earth's crust, the silicon oxygen bond.