Dynamic Heterogeneity in Random Copolymers of Polymethacrylates Bearing Different Polyhedral Oligomeric Silsesquioxane Moieties (POSS)

Abstract

Random copolymersusually considered as dynamically homogeneous with a single glass temperaturecan show dynamic heterogeneity by appropriate choice of their repeat units. Random copolymers based on polymethacrylates with polyhedral oligomeric silsesquioxane (POSS) moieties as side groups substituted with seven isobutyl ((i-Bu)7POSS-OSiMe2(CH2)3-MA) and 2,4,4-trimethylpentyl ((i-C8H17)7POSS-OSiMe2(CH2)3-MA) groups were synthesized and studied by dielectric spectroscopy, density functional theory, differential scanning calorimetry, and rheology. Two distinct relaxation processes were found by dielectric spectroscopy giving rise to two glass temperatures. In addition, rheology revealed significant broadening of the viscoelastic functions leading eventually to the failure of time–temperature superposition for all copolymer compositions. These results provide signatures of dynamic heterogeneity in a random copolymer.

Dynamical Correlations for Statistical Copolymers from High-Throughput Broad-Band Dielectric Spectroscopy

“…Each figure corresponds to a specific concentration of the third component. In polymer blends − and some statistical copolymer systems with high sequence length, localized concentration fluctuations result in the failure of the Fox prediction based on the bulk concentrations. In those cases, for the Fox equation to hold, the bulk concentrations have to be converted into effective concentrations based on the LM self-concentration model. , In our binary and ternary copolymer systems, the RAFT copolymerization among these monomers possesses a reactivity ratio close to unity, and the resulting copolymers have relatively alternating backbones.…”

“…Each figure corresponds to a specific concentration of the third component. In polymer blends 36−42 and some statistical copolymer systems 54 with high sequence length, localized concentration fluctuations result in the failure of the Fox prediction based on the bulk concentrations. In those cases, for the Fox equation to hold, the bulk concentrations have to be converted into effective concentrations based on the LM self-concentration model.…”

Phase‐separated structures of random methacrylate copolymers with pendant POSS moieties

“…The number‐average molecular weight determined by GPC and GPC MALLS showed large difference. The anomalous behavior is found from polymers with POSS in the side chain …”

“…The anomalous behavior is found from polymers with POSS in the side chain. 24,37 Glass-transition temperatures (T g s) of the random copolymers are also estimated by DSC to be shown in Table I. P(PhPOSSMA) homopolymer did not show T g below 250 C. The T g s of the PBMA and PMMA homopolymers are reported in the references as 20 C 38 and 105 C, 39 respectively.…”

Copper Wire–Catalyzed RDRP in Nonpolar Media as a Route to Ultrahigh Molecular Weight Organic–Inorganic Hybrid Polymers

“…A special class of POSS molecules is represented by POSS monomers that incorporate polymerizable double bonds in their structure. POSS monomers can be employed for attaining uniform distribution of POSS units throughout a polymeric matrix or, importantly, also for tailoring advanced hybrid materials through various controlled polymerization techniques . For instance, POSS‐based block copolymers are of interest since the presence of the bulky POSS groups leads to materials with peculiar self‐assembly behavior that can find use in applications such as lithography, drug delivery, or fabrication of superhydrophobic surfaces .…”