%0 Journal Article %A Byard, Sarah J. %A Williams, Mark %A McKenzie, Beulah E. %A Blanazs, Adam %A Armes, Steven P. %D 2017 %T Preparation and Cross-Linking of All-Acrylamide Diblock Copolymer Nano-Objects via Polymerization-Induced Self-Assembly in Aqueous Solution %U https://acs.figshare.com/articles/journal_contribution/Preparation_and_Cross-Linking_of_All-Acrylamide_Diblock_Copolymer_Nano-Objects_via_Polymerization-Induced_Self-Assembly_in_Aqueous_Solution/4650157 %R 10.1021/acs.macromol.6b02643.s001 %2 https://acs.figshare.com/ndownloader/files/7580533 %K ADH %K FT-IR %K chain transfer agents %K All-Acrylamide Diblock Copolymer Nano-Objects %K DLS %K PISA %K TEM %K PDMAC %K solution pH %K DP %K ketone-functionalized PDAAM chains %X Various carboxylic acid-functionalized poly­(N,N-dimethylacrylamide) (PDMAC) macromolecular chain transfer agents (macro-CTAs) were chain-extended with diacetone acrylamide (DAAM) by reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization at 70 °C and 20% w/w solids to produce a series of PDMAC–PDAAM diblock copolymer nano-objects via polymerization-induced self-assembly (PISA). TEM studies indicate that a PDMAC macro-CTA with a mean degree of polymerization (DP) of 68 or higher results in the formation of well-defined spherical nanoparticles with mean diameters ranging from 40 to 150 nm. In contrast, either highly anisotropic worms or polydisperse vesicles are formed when relatively short macro-CTAs (DP = 40–58) are used. A phase diagram was constructed to enable accurate targeting of pure copolymer morphologies. Dynamic light scattering (DLS) and aqueous electrophoresis studies indicated that in most cases these PDMAC–PDAAM nano-objects are surprisingly resistant to changes in either solution pH or temperature. However, PDMAC40–PDAAM99 worms do undergo partial dissociation to form a mixture of relatively short worms and spheres on adjusting the solution pH from pH 2–3 to around pH 9 at 20 °C. Moreover, a change in copolymer morphology from worms to a mixture of short worms and vesicles was observed by DLS and TEM on heating this worm dispersion to 50 °C. Postpolymerization cross-linking of concentrated aqueous dispersions of PDMAC–PDAAM spheres, worms, or vesicles was performed at ambient temperature using adipic acid dihydrazide (ADH), which reacts with the hydrophobic ketone-functionalized PDAAM chains. The formation of hydrazone groups was monitored by FT-IR spectroscopy and afforded covalently stabilized nano-objects that remained intact on exposure to methanol, which is a good solvent for both blocks. Rheological studies indicated that the cross-linked worms formed a stronger gel compared to linear precursor worms. %I ACS Publications