Structural Study of Four-Armed Amphiphilic Star-Block Copolymers: Pristine and End-Linked Tetronic T1307

Abstract

We present a comparative structural study of 30 wt % aqueous suspensions of two related systems based on 4-arm PEO−PPO type of macromolecules (Tetronic T1307, BASF) with the PPO block near the star center. One system concerns the pristine 4-arm PEO−PPO star block copolymer T1307. The second system is a 1:1 blend consisting of, respectively, tetraamine (TAT) and tetra-N-hydroxysuccinimide (TNT) terminated T1307. The two systems show common characteristics which are also known from linear PEO−PPO type of copolymers (Pluronic, BASF): at low temperatures the measured structure is dominated by the characteristics of individual molecules, while at higher temperatures hydrophobic effects of the PPO domains cause self-assembly into spherical or rodlike micelles. These micelles form in both systems ordered mesophases. The pristine T1307 copolymer suspension behaves generally very similarly to linear PEO−PPO type of di-and triblock copolymers: unimers at low temperatures associating into micelles at higher temperatures, forming subsequently cubic and hexagonal phases upon further increase in temperatures. The cubic phase of the 30 wt % Tetronic T1307 has FCC symmetry. The structure of the crosslinked 30 wt % 1:1 TAT−TNT system is basically organized into two-dimensional network sheets. At low temperatures the system is rather disordered but still with a sharp correlation peak which is associated with the distance between neighboring network sheets. Upon raising temperatures, PPO self-assembly causes organization across neighboring sheets, resulting in cylinder-like assemblies perpendicular to the sheets. These cylinders form hexagonal structure.

Amphiphilic Polymer Conetworks Based on Interconnected Hydrophobic Star Block Copolymers: Synthesis and Characterization

“…2, and S(q) is the structure factor of the system, 1 N the number density of scattering domains, and A a factor that takes into account that the networks had to be filled as granular material into the cuvettes and partly there was also not sufficient material to completely fill the cuvettes ( A was determined from the incoherent background that arises largely from the H atoms of the polymer). It might be noted that this type of modeling was also successful for describing similar systems, as, for instance, amphiphilic polydimethylsiloxane − poly(ethylene glycol) (PDMS‐PEG) conetworks, cross‐linked star polymers or Tetronic‐based amphiphilic star‐block copolymers . SLD agg and SLD solv are the scattering lengths of domain and solvent, respectively, and R sph the sphere radius.…”

“…It might be noted that this type of modeling was also successful for describing similar systems, as, for instance, amphiphilic polydimethylsiloxane À poly(ethylene glycol) (PDMS-PEG) conetworks, [27] cross-linked star polymers [24] or Tetronic-based amphiphilic star-block copolymers. [28] SLD agg and SLD solv are the scattering lengths of domain and solvent, respectively, and R sph the sphere radius. For SLD agg we just assumed polyMMA with a density of 1.18 g/mL and for SLD solv the presence of D 2 O and the hydrophilic chains of the polymer (as well as the hydrophobic chains not contained in the aggregates).…”

“…The more compact nature and the usually large molecular weight of star polymers are expected to introduce fewer network defects related to chain entanglements, and, therefore, allow for more regular organization of the nanophases in the phase separated state. Although most of the APCNs already prepared from amphiphilic star block copolymers presented nanophase separation with only short‐range order, some recent reports revealed morphologies with longer‐range order . In these latter reports, a rather low amount of cross‐linker was used, so as to allow more freedom to the polymer segments to reach a lowest‐energy configuration, resulting in the formation of better‐ordered morphologies within the APCNs.…”

“…Although most of the APCNs already prepared from amphiphilic star block copolymers presented nanophase separation with only shortrange order, [20][21][22][23][24][25][26] some recent reports revealed morphologies with longer-range order. [27][28][29] In these latter reports, a rather low amount of cross-linker was used, so as to allow more freedom to the polymer segments to reach a lowestenergy configuration, resulting in the formation of better-ordered morphologies within the APCNs. Thus, in the present study, a lower-than-usual cross-linker loading was employed too, together with a higher hydrophobic content in most samples.…”

Glycine elicited self-assembly of amphiphilic star block copolymers with contradistinct hydrophobicities

“…Linear ABA type triblock copolymers (Pluronics ® ) comprise of poly (ethylene oxide) (PEO) and poly (propylene oxide) (PPO) blocks arranged end to end and have been extensively studied from viewpoint of their aqueous solution behaviour [4][5][6][7][8][9]. Tetronics ® , with an X-shaped structure made of an ethylene diamine central group bonded to four chains of PEO-PPO blocks are barely examined [10][11][12][13][14][15][16]. The unique structure of Tetronics ® imparts them with multistimuli responsiveness.…”