2 research outputs found
Versatile Synthesis of Amine-Reactive Microgels by Self-Assembly of Azlactone-Containing Block Copolymers
Relations
between molecular design, chemical functionality, and
stimulus-triggered response are important for a variety of applications
of polymeric systems. Here, reactive amphiphilic block copolymers
(BCPs) of polyÂ(2-vinylpyridine)-<i>block</i>-polyÂ(2-vinyl-4,4-dimethylÂazlactone)
(PVP-<i>b</i>-PVDMA) were synthesized and assembled into
microgels capable of incorporating functional amines. The composition
of the PVP-<i>b</i>-PVDMA BCPs was varied to control the
number of reactive sites in the spherical aggregates created by self-assembly
of PVP-<i>b</i>-PVDMA BCPs in a 2-propanol/THF (v:v = 19:1)
solvent mixture, which is selective for PVP. PVDMA and PVP segments
were selectively cross-linked by 1,4-diaminobutane (DAB) or 1,4-diiodobutane
(DIB) to fabricate core- and corona-cross-linked azlactone-containing
microgels, respectively. Non-cross-linked aggregates of PVP-<i>b</i>-PVDMA and DIB-cross-linked microgels dissociate when exposed
to THF, which is a good solvent for both blocks. However, the DAB-cross-linked
BCP microgels swell in THF, suggesting the formation of a stable,
three-dimensional network structure. Because of their ability to be
reactively modified in ways that allows their stability or disassembly
characteristics to be tailored, these azlactone-containing BCP microgels
provide an attractive platform for applications in a wide range of
fields, including catalysis, imaging, molecule separation, and guest
loading for targeted delivery
Control of Self-Assembled Structure through Architecturally and Compositionally Complex Block Copolymer Surfactant Mixtures
The self-assembly of binary mixtures
of architecturally and compositionally
diverse surfactant-like polystyrene–polyÂ(2-vinylpyridine) (PS–PVP)
block copolymers (BCPs) in solution and in thin films has been systematically
studied. PS–PVP BCPs of different molecular architecture synthesized
by living anionic polymerization, including linear diblocks, triblocks,
and branched star-like copolymers all having different block sizes,
styrene to 2-vinylpyridine ratios, and variations in numbers of arms,
were employed as constituent building blocks for the construction
of advanced copolymeric ensembles. While ensembles formed from monomodal
PS–PVP BCPs exhibit simple spherical aggregate structures in
the PS-selective solvent toluene, aggregates created by mixing PS–PVP
BCPs of different architecture display structures that include spherical,
worm-like and large compound micellar aggregates. This result is attributed
to the complex, architecture-induced diversity of microphase segregation
in the mixed systems, wherein the fine-scale structures of the resultant
ensembles can be further controlled by adjusting the blend composition.
For example, unique hierarchically structured large compound micellar
aggregates with spherical primary structures and worm-like secondary
structures that resemble a brain coral were directly created when
a 1:1 mixture (by weight) of a triblock copolymer and a star BCP that
was cast in thin film form. The present study is valuable for illuminating
the range of structures that may be created through architecture-
and composition-controlled self-assembly of amphiphilic copolymer
mixtures, which generally benefits the development of self-assembly
as a method to make soft matter building blocks, as well as connections
between self-assembled structures in solution and their thin films