Acid-Labile Surfactants Based on Poly(ethylene glycol), Carbon Dioxide and Propylene Oxide: Miniemulsion Polymerization and Degradation Studies

Abstract

Partially degradable, nonionic AB and ABA type di-and triblock copolymers based on poly(propylene carbonate) and poly(ethylene glycol) blocks were synthesized via immortal copolymerization of carbon dioxide and propylene oxide, using mPEG or PEG as a macroinitiator, and (R,R)-(salcy)-CoOBzF 5 as a catalyst in a solvent-free one-pot procedure. The amphiphilic surfactants were prepared with molecular weights (M n ) between 2800 and 10,000 g·mol −1 with narrow molecular weight distributions (1.03-1.09). The copolymers were characterized using 1 H-, 13 C-and DOSY-NMR spectroscopy and size exclusion chromatography (SEC). Surface-active properties were determined by surface tension measurements (critical micelle concentration, CMC; CMC range: 1-14 mg·mL −1 ). Degradation of the acid-labile polycarbonate blocks was investigated in aqueous solution using online 1 H-NMR spectroscopy and SEC. The amphiphilic polymers were used as surfactants in a direct miniemulsion polymerization for poly(styrene) (PS) nanoparticles with mean diameter of 270 to 940 nm. The usage of an acid-triggered precipitation of the emulsion simplified the separation of the particles from the surfactant and purification of the nanoparticles.

Catalytic Chain Transfer Copolymerization of Propylene Oxide and CO2 using Zinc Glutarate Catalyst

“…Control over the molecular weight may be desirable, e. g . for use in water‐based dispersions or the application as polyol compound in polyurethane manufacturing . Regulation of the molecular weight can be reached by the treatment of high‐molecular weight products with acids or alcohols resulting in a controlled polymer degradation .…”

Surfactant-Emulating Amphiphilic Polycarbonates and Other Functional Polycarbonates through Metal-Free Copolymerization of CO2 with Ethylene Oxide

“…Taking advantage of a TEB-mediated initiating system that works for EO/CO 2 copolymerization and ROP of EO as well, triblock copolymers with structures similar to the PEO- b -PPO- b -PEO surfactant could be derived in one pot as shown in Scheme B: after copolymerizing EO with CO 2 using TBAS as the difunctional initiator under the conditions described above (entry 10 in Table ), the ROP of EO could be subsequently undertaken after releasing CO 2 and charging an additional EO monomer. CO 2 -based amphiphilic copolymers were prepared in the past through immortal CO 2 /epoxide copolymerization in the presence of macrotransfer agents such as ω-hydroxyl terminated PEO or α,ω-dihydroxyl terminated PEO: − in this type of PEO- b -PPC diblock or PPC- b -PEO- b -PPC triblock structures, the amphiphilic copolymers obtained do not include a central hydrophobic block like in regular surfactants (PEO- b -PPO- b -PEO). To the best of our knowledge, nonionic surfactants made of two external PEO hydrophilic blocks and a central hydrophobic CO 2 -based polycarbonate have not been reported before.…”

“…57 It can thus be concluded that PECEO is more hydrophobic than PPO, and the incorporated amount of EO (9 mol %) does not affect much its hydrophobic nature. In addition, triblock copolymers such as PPC-b-PEO-b-PPC with similar HLB values (9.9) are not water soluble, 53 which emphasizes the influence of the overall surfactant structure on its micellar behavior. Increasing the weight fraction of hydrophilic PEO from 45 to 65% in P(EO-ECEO-EO) 2 resulted in an increase of the cmc value to 0.081 g/L.…”

“…Such sequential (co)­polymerization afforded amphiphilic PEO- b -PECEO- b -PEO triblock copolymers (Scheme B), emulating well-known, commercial nonionic surfactants. In comparison to its commercial homologs Poloxamers or Pluronics (PEO- b -PPO- b -PEO), , the use of inexpensive and abundant CO 2 to generate potential surfactants that are degradable is expected to reap environmental benefits from the standpoint of the final metabolites generated upon its biodegradation. − Lastly, upon adjusting the polymerization pressure of CO 2 , degradable PEO-like PEOEC with very low carbonate content (∼5 mol %) could be generated (Scheme C); in addition, a functional epoxide such as allyl glycidyl ether (AGE) was terpolymerized with EO and CO 2 to introduce functional groups along the copolymer backbone for subsequent conjugation as a drug delivery vehicle. It should be noted that, in all cases, the EO-based polymers produced do not contain any metal residues, clearing any concern for applications as biomaterials and surfactants for home and personal care.…”

Functional Polycarbonates from Carbon Dioxide and Tailored Epoxide Monomers: Degradable Materials and Their Application Potential

“…Only cyclic carbonates and the corresponding diol were obtained after degradation of the polycarbonate block. The authors used the degradation to simplify the separation method of surfactants and polystyrene nanoparticles after a miniemulsion polymerization …”