The combination of reversible chain transfer chemistry with highly orthogonal [2 + 3] cycloadditions ('click chemistry') allows for the synthesis of well-defined block copolymers of monomers with extremely disparate reactivities.

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"Schizophrenic" diblock copolymers containing nonionic and zwitterionic blocks were prepared with well-controlled molecular weights via atom-transfer radical polymerization (ATRP). In this work, we report a systematic study of how morphological changes of poly(N-isopropylacrylamide)-block-poly(sulfobetaine methacrylate) (PNIPAAm-b-PSBMA) copolymers affect hemocompatibility in human blood solution. The "schizophrenic" behavior of PNIPAAm-b-PSBMA was observed by (1)H NMR, dynamic light scattering (DLS), and turbidity measurement with double morphological transition, exhibiting both lower critical solution temperature (LCST) and upper critical solution temperature (UCST) in aqueous solution. Below the UCST of PSBMA block, micelles were obtained with a core of insoluble PSBMA association and a shell of soluble PNIPAAm, whereas the opposite micelle structure was observed above the LCST of PNIPAAm block. In between the UCST and LCST, unimers with both soluble blocks were detected. Hydrodynamic size of prepared polymers and copolymers is determined to illustrate the correlations between intermolecular nonionic/zwitterionic associations and blood compatibility of PNIPAAm, PNIPAAm-b-PSBMA, and PSBMA suspension in human blood. Human fibrinogen adsorption onto the PNIPAAm-b-PSBMA copolymers from single-protein solutions was measured by DLS to determine the nonfouling stability of copolymer suspension. The new nonfouling nature of PNIPAAm-b-PSBMA copolymers was demonstrated to show extremely high anticoagulant activity and antihemolytic activity in human blood over a wide range of explored temperatures from 4 to 40 °C. The temperature-independent blood compatibility of nonionic/zwitterionic block copolymer along with their schizophrenic phase behavior in aqueous solution suggests their potential in blood-contacting applications.

Propargyl methacrylate with its acetylene function protected with a silyl group is polymerized via the reversible addition fragmentation chain transfer (RAFT) process, using cyanoisopropyl dithiobenzoate (CPDB) as RAFT agent, and subsequently deprotected to afford a polymer backbone where each repeated unit is decorated with an acetylene functionality (1000 < Mn < 13,600 g mol−1, 1.07 < PDI < 1.29). In parallel, an azide functionalized xanthate (ethoxythiocarbonylsulfanyl‐acetic acid 3‐azido‐propyl ester) was employed to prepare narrow polydisperse poly(vinyl acetate) (Mn = 850 g mol−1, PDI = 1.20). The two polymers are conjugated by Huisgen 1,3‐dipolar cycloaddition to afford narrow polydisperse comb polymer (1.12 < PDI < 1.18, 3400 < Mn < 12,500 g mol−1, based on linear polystyrene calibration, 4500 < M < 15,600 g mol−1). The study places special emphasis on following the copper catalyzed 1,3‐dipolar cycloaddition via Fourier Transform Infrared Spectroscopy (FTIR) as well as via on‐line UV–Vis photospectrometry on several model compounds, i.e. the nonmonomer inserted azido‐xanthate RAFT/MADIX agent as well as a 2‐propargyl‐2‐bromopropionate and 3‐azidopropyl‐2‐bromopropionate model compounds. A suitable absorption band in the VIS at 666 nm (tentatively assigned to a charge transfer complex between copper(I) and the forming triazole moieties) is identified as a promising sensor for following the click reaction kinetics, thus allowing for the rapid assessment of reaction completion in an on‐line fashion. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 155–173, 2008

The present communication explores a novel avenue to glycopolymer-block-poly(vinyl acetate) polymers by a combination of reversible addition fragmentation chain transfer (RAFT) chemistry and Huisgen 1,3-dipolar cycloaddition (i.e., so-called ‘click’ chemistry) under mild reaction conditions. Such block copolymers are—because of the strongly disparate reactivity of the two monomers—otherwise not obtainable. Poly(vinyl acetate) that has an azide end group (Mn 6800 g mol–1, PDI 1.15) was treated with poly(6-O-methacryloyl mannose) (Mn 7600 g mol–1, PDI 1.11) in the presence of 1,8-diaza[5,4,0]bicycloundec-7-ene and copper(i) iodide. The resulting poly(vinyl acetate)-block-poly(6-O-methacryloyl mannose) had a number-average molecular weight of 15400 g mol–1 and a PDI of 1.48, which indicates that while the cycloaddition had occurred the resulting polymer distribution featured a considerable width. The resulting slightly amphiphilic block copolymer was subsequently investigated with regard to its self-assembly in aqueous solution. Dynamic light scattering studies indicated a hydrodynamic diameter of close to 200 nm. Transmission electron microscopy studies indicate the formation of rods as well as spheres with transitions between these two phases. However, the segregation between core and shell in the spheres is not pronounced; such behaviour is expected for weakly amphiphilic block copolymers.

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