Statics and Dynamics of .omega.-Functionalized Block Copolymers of Styrene and Isoprene

Abstract

The statics and dynamics of cw-functionalized diblock copolymers of styrene and isoprene have been studied with small-angle X-ray scattering (SAXS) and with rheology and dielectric spectroscopy. The asymmetric diblock copolymers (wps «= 30%) had a dimethylamino or zwitterion group at either end of the chain, and the molecular weights were in the range (0.62-2.44) x 104. Depending on the temperature, the SAXS results revealed two separate levels of microphase separation, one between the polystyrene (PS) and polyisoprene (PI) blocks forming the microdomain structure and another one between ionic and nonionic material. The latter process creates sufficient contrast notwithstanding the small fraction of the zwitterionic groups. When the zwitterion is linked to the PI chain end, aggregates are formed at low temperatures within the PI phase. These aggregates manifest themselves both in rheology and in dielectric spectroscopy, respectively, with an extended rubbery plateau and with a new dielectric process associated with restricted PI segmental relaxation. When the zwitterion is located on the PS chain end, association takes place, at high temperatures, within the PS phase and acts to stabilize the new microdomain up to very high temperatures. When compared with neutral diblocks, the co-functionalized diblock copolymers constitute a new class of materials which provide the possibility of altering the phase behavior by introducing a small amount of a polar group at one chain end.

Effect of Zwitterion Substitution on the Structure and Dynamics of Asymmetrically Substituted Polystyrene-block-polyisoprene Diblock and Triblock Copolymers

“…This situation in the symmetric copolymers is in sharp contrast to the asymmetric case studied earlier. [12,13] In the asymmetric copolymers an additional broad reflection was found corresponding to correlations between ionic aggregates with a spacing smaller than the periodicity of the (hexagonal) lattice. In the present case, an aggregation peak is absent implying weak correlations between aggregates and/or much smaller distances.…”

“…The conversion of the amine block copolymers to the sulfo-zwitterion derivatives was achieved by reaction with cyclopropanesultone as described in detail elsewhere. [12] Characterization The copolymers were extensively characterized by a variety of methods. Molecular weight distributions and homogeneity of final, and intermediate, products were determined by size exclusion chromatography (SEC).…”

“…In the past we reported on the phase state and dynamics of (i) cylinder-forming asymmetrically functionalized diblock copolymers (P(S-b-I)) of the SIZw and ZwSI type, [12,13] and (ii) lamellar-forming SZwI copolymers, [14] with the same functional group Zw (zwitterion) and hydrocarbon blocks S (polystyrene) and I (polyisoprene). For the cylinder-forming asymmetrically functionalized diblock copolymers of the type ZwIS and ZwSI we found [12,13] that the zwitterion induces an additional level of phase separation, namely between the ionic groups and hydrocarbon material which is on top of the microphase separation between the incompatible hydrocarbon blocks. The presence of the short zwitterion group next to the PS block was found to stabilize the ordered structures, and to form multiplets within the PS phase which was also treated theoretically.…”

Synthesis of block co-polymers and star-branched polymers consisting of conducting polyacetylene segments via ionic interaction to form ionic bonds

“…For example, it was found that the terminal tertiary amine of polymer A forms ionic bond with either of the terminal sulfonic acid or carboxylic acid of polymer B to afford the AB block co-polymers [36,37]. The morphologies of the block co-polymers thus obtained resemble closely those found with the corresponding covalently bonded block co-polymers [38][39][40][41]. Very recently, Hadjichristidis and co-workers have reported the synthesis of four-arm asym- Chain-end-functionalities were more than 95% in all samples.…”

Model ω‐Functionalized Linear Polystyrenes with One, Two, and Three Sulfobetaine End Groups: Synthesis, Characterization, and Association Behavior

“…[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Additionally, a number of fundamental studies aimed at the elucidation of physical phenomena like block copolymer phase behavior, polymer adsorption, adsorbed polymer brush structure, and colloid stabilization and so on were made possible through the use of end-functionalized polymers. [26][27][28][29][30][31][32][33][34][35][36] Nature, number, and position of the end groups have been varied in different ways as well as the nature of the polymeric chain. Particular attention has been paid to the case of polymers bearing zwitterionic sulfobetaine groups.…”