Thermoresponsive Poly(N-C3 glycine)s

Abstract

Ring-opening polymerization of N-substituted glycine Ncarboxyanhydrides (NCAs) was applied to prepare a series of welldefined poly(N-C3 glycine)s (C3 = n-propyl, allyl, propargyl, and isopropyl), polypeptoids, with molecular weights in the range of 1.8−6.6 kg mol −1 . Poly(N-isopropyl glycine), a previously unreported polypeptoid, could be obtained by bulk polymerization of the corresponding NCA in the melt. The samples were characterized by spectroscopy (NMR and FT-IR), size exclusion chromatography (SEC), and matrixassisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI−ToF MS). The polymers could be dispersed in water up to 20−40 g L −1 ; the poly(N-propargyl glycine) was not soluble in water. Turbidity measurements of the three water-soluble polypeptoids illustrated cloud point temperatures dependent on structural and electronic properties of the side chain. The cloud point temperatures were found to increase in the order C3 = n-propyl (15−25 °C) < allyl (27−54 °C) < isopropyl (47−58 °C). Long-term annealing of the aqueous solution of poly(N-{n-propyl} glycine) and poly(N-allyl glycine) above the cloud point temperature resulted in the formation of crystalline microparticles with melting points of 188−198 and 157−165 °C (differential scanning calorimetry, DSC), respectively, and rose bud type morphology (scanning electron microscopy, SEM).

Thermal Properties of Aliphatic Polypeptoids

“…In particular, the successful preparation of a pentablock quinquiespolymer highlighted the unique character of the NNCA NuLROP [23]. Moreover, efficient polymer analogue modification [24,25] and thermo-responsiveness [26,27] of polypeptoids was described.…”

Polypeptoid polymers: Synthesis, characterization, and properties

“…[15][16][17][18][19][20] The relative cell viability was found to be dependent on the polymer composition and concentration. It was found that relative cell viability decreases with increasing polymer concentration for all polymers (Figure 13).…”

“…In recent years, the substrate scope for polymerization studies was further expanded to include a variety of R-NCA monomers bearing various N-substituents ( Figure 2). [5,6,[15][16][17][18][19][20][21][22] Luxenhofer et al demonstrated that the polymerizations of Me-NCAs using benzyl amine initiators were shown to proceed in a controlled manner without chain transfer or termination events, producing polysarcosines with narrow Poisson distribution (PDI < 1.1-1.3) and M n s that can be controlled by the initial monomer to initiator feed ratios. [56] The molecular distribution remains narrow (PDI 5 1.01-1.07) even after ten sequential polymerizations of Me-NCA monomers (DP < 100), attesting to the robustness of the living polymerization and suggesting the potential uses of the methods towards the synthesis of well-defined block copolypeptoids via sequential monomer addition.…”

“…The polypeptoid backbone containing tertiary amide linkages is highly polar and hydrophilic. The physicochemical properties of polypeptoids can be tailored by the N-substituent structures, enabling control over the hydrophilicity and lipophilicity balance (HLB), charge characteristics, [13,14] backbone conformation, [1][2][3][4][5][6][7][8][9][10][11][12] solubility, [15][16][17][18][19][20] thermal and crystallization properties of the polypeptoids. [21][22][23][24] Without extensive hydrogen bonding, polypeptoids are thermally processable similar to conventional thermoplastics, [20][21][22][23][24] whereas polypeptides undergo thermal degradation before they can be melt-processed due to the extensive hydrogen bonding interactions.…”

“…. [16,18,[33][34][35][36][37] N-substituted glycine precursors can also react directly with phosgene to yield R-NCA monomers. [38,39] The former methods are more popular than the latter due to the avoidance of toxic phosgene as well as the relative ease of purification to afford high purity R-NCA monomers.…”