Relaxation Processes of Poly(tert‐butyl acrylate) Chemically Confined via Hydrogen Bonds

Abstract

In this work, tailored copolymers of tert‐butyl acrylate and acrylic acid (AA) with an ABA type structure were systematically analyzed via dynamic‐mechanical analysis with regard to their relaxations, in which the main focus was put on a chemical confinement (cc) mode caused by hydrogen bonds. Four different relaxation modes were detected, whereupon two modes seem to depend on the length of the inner B‐block and one on the length of the outer A‐blocks. One mode below room temperature could be identified as a secondary relaxation which belongs to the B‐block and is most likely induced by a cc. A softening of the polymer corresponding to the glass transition is found near to room temperature and surprisingly shifts to lower temperatures with increasing chain length of the B‐block. A second softening of the ABA type copolymers is caused by the AA containing A‐blocks and was found at higher temperatures.magnified image

Biomimetic triblock and multiblock copolymers containing l‐Phenylalanine moieties showing healing and enhanced mechanical properties

“…The T g is, in all copolymers, elevated by several degrees compared with that of pure poly‐MA, which indicates that APA blocks confine the inner MA block and thus lower the chain mobility. Such an effect has been found earlier via mechanical spectroscopy in similar triblock copolymers carrying less‐effective H‐bonding groups from acrylic acid in their outer block domains . A high temperature transition can be observed in the multiblock copolymer samples, which most likely corresponds to the glass transition of APA domains.…”

Gamma relaxation in bulk metallic glasses

“…Here we provide strong evidence for the existence of a general third structural relaxation mechanism in metallic glasses, which we observe in three glass forming alloys at around 0.2Tg-0.3Tg. This low temperature relaxation is very akin to the long known -relaxation in amorphous polymers, where it has been reported, for instance, in co-blockpolymers [18], epoxy resins [19,20] and substituted polystyrenes [21].…”

Multiblock Copolymers of Styrene and Butyl Acrylate via Polytrithiocarbonate-Mediated RAFT Polymerization

“…It seems promising to mimic this motif and prepare multiblock copolymers that comprise hydrogen bonding segments [13]. It has already been shown by us and others that these polymers have distinct mechanical properties compared to the corresponding polymers without hydrogen bonding segments [14,15].…”