The 2‐chloropropionamide derivative featuring an azido group is used as the initiator for the ATRP of N‐isopropylacrylamide (NIPAM) with copper(I) chloride (CuCl) and tris[2‐(dimethylamino)ethyl]amine (Me6TREN) to produce the PNIPAM end‐functionalized with an azido group. Subsequently, the ‘click’ reaction between the azido end‐group and acetylene derivatives is demonstrated to produce PNIPAM in which the end‐groups are modified by the phenyl, 4‐phenoxyphenyl, butyl, octyl, carboxylic acid, and hydroxymethyl groups. The resulting PNIPAM derivatives show a LCST that ranges from 34.8 to 44.6 °C depending on the introduced end‐group.magnified image

This work discusses the self-assembly properties of thermoresponsive hybrid oligosaccharide-block-poly(N-isopropylacrylamide) copolymer systems: maltoheptaose-block-poly(N-isopropylacrylamide) (Mal(7)-b-PNIPAM(n)) copolymers. Those systems at different molar masses and volume fractions were synthesized using Cu(I)-catalyzed 1,3-dipolar azide/alkyne cycloaddition, so-called "click" chemistry, between an alkynyl-functionalized maltoheptaose (1) and poly(N-isopropylacrylamide) having a terminal azido group (N(3)-PNIPAM(n)) prepared by atom transfer radical polymerization (ATRP). While the cloud point (T(cp)) of the N(3)-PNIPAM(n) ranged from 36.4 to 51.5 degrees C depending on the degree of polymerization, those obtained of the diblock copolymers ranged from 39.4 to 73.9 degrees C. The self-assembly of such systems is favored due to the hydrophobicity of the PNIPAM in water above the T(cp). While the N(3)-PNIPAM(n) present polydisperse globular shape with a mean diameter of 500 nm, well-defined vesicular morphologies with an approximate diameter of 300 nm are obtained in diblock copolymer systems. These results were obtained and confirmed using static and dynamic light scattering as well as imaging techniques such as transmission electron microscope experiments.

Organocatalytic controlled/living ring-opening polymerization of cyclotrisiloxanes using water as an initiator and strong organic bases as catalysts produced a variety of linear polysiloxanes with narrow polydispersity and well-defined symmetric structures.

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Organic superbases, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), proazaphosphatranes (P(RNCH2CH2)3N: R = CH3, TMP; R = i-Bu, TiBP), and phosphazene bases (1-tert-butyl-2,2,4,4,4-pentakis(dimethylamino)-2Λ5,4Λ5-catenadi(phosphazene), t-Bu-P2; 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phosphoranylidenamino]-2Λ5,4Λ5-catenadi(phosphazene), t-Bu-P4) were employed to determine the catalytic activity in the group transfer polymerization (GTP) of methyl methacrylate (MMA). Among the superbases used, TiBP and t-Bu-P4 effectively catalyzed the polymerization to afford poly(methyl methacrylate) (PMMA) with controlled molecular weight and narrow polydispersity. In particular, the molecular weight of the PMMA obtained from the t-Bu-P4-catalyzed GTP was up to 109 600 g mol–1. Only one series of peaks was observed in the MALDI–TOF MS spectra of the PMMAs obtained from the TiBP- and t-Bu-P4-catalyzed GTPs, indicating that both polymerizations proceeded without any side reactions. A postpolymerization experiment further supported the living nature of the TiBP- and t-Bu-P4-catalyzed GTPs of MMA. Furthermore, a mechanistic study of the TiBP- and t-Bu-P4-catalyzed GTPs of MMA was attempted by determining the stereoregularity of the obtained PMMAs and obtaining a series of NMR spectra for the equimolar mixtures of MTS and TiBP or t-Bu-P4.