Thermodynamics of Chain Architecture in Acrylic Block Terpolymers

Abstract

In this article, we report the manipulation of block terpolymer morphology through control of the segment distribution. We consider a model system comprised of three acrylic monomers: hydrophilic poly(hydroxyethyl acrylate) (H), hydrophobic poly(octyl acrylate) (O), and polar poly(methyl acrylate) (M). For each of four chemical compositions, we altered the M segment distribution in four terpolymer architectures with reversible addition–fragmentation chain transfer (RAFT) polymerization to yield: two triblock terpolymer architectures, HOM and HMO, and two diblock terpolymer architectures, HM/O and H/MO, where the M segments are statistically distributed in the O or H blocks, respectively. Using a combination of small-angle X-ray scattering and dynamic shear rheology, we illustrate how the monomer distribution can be used to manipulate the thermodynamic behavior of terpolymers at constant chemical composition. These results will be of use to those wishing to partially decouple the formulation of a block copolymer from its morphology.

Gel Point Suppression in RAFT Polymerization of Pure Acrylic Cross-Linker Derived from Soybean Oil

“…Hyperbranched poly­(AESO)­s (PAESOs) were synthesized via different conditions spanning a range of monomer and initiator concentrations. ETMP as the CTA was selected in this study due to its good control of acrylic monomers, studied extensively by Bergman et al , While it is known that xanthates with R groups featuring secondary carbons struggle to mediate RAFT polymerizations, we have found that xanthates that use R groups with tertiary carbon are efficacious for acrylic monomers. The proper rate of addition–fragmentation of ETMP ensures equal probability of all chain growth, minimizing the chances of network formation by uncontrolled free radical polymerization .…”

“…Chain Transfer Agent Synthesis. Ethyl 2-(ethoxycarbonothioylthio)-2-methylpropanoate (ETMP) was synthesized following the method reported by Bergman et al 41,42 Potassium hydroxide (50 mmol) was stirred in ethanol (20 mL) at room temperature until it completely dissolved. Then carbon disulfide (10 mL) was added over 90 min, and the solution was allowed to stir for 5 h. Ethyl αbromoisobutyrate (14.8 mL) was added dropwise, and the solution was stirred for 12 h. The mixture was filtered and solvent was removed by rotary evaporation.…”

Gelation Suppression in RAFT Polymerization

“…Experimental gel conversions X g,exp (filled symbols) and Flory–Stockmeyer predicted gel conversions X g FS (opened symbols) vs crosslinking tendency for this work (▼, ▽), our previous work of poly­(acrylated epoxidized soybean oil) (PAESO) (▲, △), other RAFT (◆, ◇), and ATRP (●, ○) in the literature. ,− X g FS is calculated based on eq . The experimental gel conversions in region I are related to CT by X g,exp = 141.65 – 60 log­(CT) with r 2 = 0.85.…”

Thermoplastic Elastomers from Vegetable Oils via Reversible Addition-Fragmentation Chain Transfer Polymerization

“…The procedure below is analogous to the method described by Bergman et al (31) Potassium hydroxide (0.05 mol) was stirred in ethanol (20 mL) at room temperature until completely dissolved. Carbon disulfide (10 mL) was then added over 90 minutes, and the solution was allowed to stir for five hours.…”