Sub-Rouse Dynamics in Poly(isobutylene) as a Function of Molar Mass

Stereoregular poly(cyclohexene carbonate) (PCHC) homopolymers were prepared via copolymerization of cyclohexene oxide and carbon dioxide (CO2) using (R,R)-(salcy)-CoCl and bis(triphenylphosphine)iminium chloride as a catalyst. The homopolymers had molar masses in the range of 4800–33,000 g mol–1 and relatively narrow dispersity after careful fractionation, as required for the molecular dynamics investigation. We employed differential scanning calorimetry and dielectric spectroscopy, the latter as a function of temperature and pressure, for investigating the thermal properties and the molecular dynamics, respectively. The segmental dynamics in the vicinity of the liquid-to-glass temperature was very complex. The dual segmental processes were inseparable by decreasing the temperature or by increasing the pressure. Based on DFT calculations of the dipole moment, they were ascribed to different stereo sequences of the PCHC backbone. The limiting glass temperature, T g, for very high molar masses was ∼125 °C. The high T g value obtained herein well justifies its application as a CO2-based alternative for polystyrene (PS) in a variety of materials based on block copolymers. Moreover, fragility increased with increasing molar mass with values intermediate to poly(styrene) and poly(cyclohexyl methacrylate). The flexible cyclohexyl group in PCHC undergoing intramolecular chair-to-chair conversion increases the packing ability and consequently decreases the fragility. PCHC is a brittle material because it lacks entanglements even for the higher molar masses investigated herein, which is relevant for application as a PS substitute. Within the investigated range of molar masses, the dependences of the terminal relaxation times, τΝΜ, and of the zero-shear viscosity, ηο, on the molar mass, M, are τΝΜ/τSM ∼ M 3.2 and ηο ∼ M 1.4, revealing an intermediate behavior between Rouse and entangled chains.

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“…A similar relaxation process was observed in PCHMA . Such sub- T g processes are common among glass-forming polymers. , …”

Section: Results and Discussionsupporting

confidence: 73%

“…38 Such sub-T g processes are common among glass-forming polymers. 51,52 Viscoelastic Properties. High T g and tough materials require entangled chains.…”

Section: T H Imentioning

confidence: 99%

Dynamics of Poly(cyclohexene carbonate) as a Function of Molar Mass

Spyridakou

Gardiner

Papamokos

et al. 2022

ACS Appl. Polym. Mater.

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“…Here, the choice of the flexible polymer is poly(isobutylene) (T g ∼ 200 K). 56 In particular, we explore the effect of its high mobility on the PBLG self-assembly and dynamics. The presence of a second block can have consequences on the self-assembly and stability of PBLG αhelices and on the concomitant dynamics.…”

Section: Resultsmentioning

confidence: 99%

“…Earlier studies on copolymers containing PBLG with amorphous polymers (e.g., polybutadiene, ,, polystyrene, ,,, poly(ethylene oxide), , polyisoprene, poly(dimethylsiloxane), , and poly(9,9-dihexylfluorene-2,7-diyl)) reported nanophase separation to phase mixing depending on the value of the interaction parameter and the particular architecture. Here, the choice of the flexible polymer is poly(isobutylene) ( T g ∼ 200 K) . In particular, we explore the effect of its high mobility on the PBLG self-assembly and dynamics.…”

Section: Resultsmentioning

confidence: 99%

“…A characteristic GPC of PBLG is shown in Figure S1. To prepare PIB- b -PBLG copolymers, PIB was first synthesized by living cationic polymerization , and end-capped with methallyltrimethylsilane (MATMS) to yield olefin-terminated PIB. Sequentially, PIB-NH 2 was synthesized by reacting PIB-olefin with 2-( Boc -amino)ethanethiol via UV-mediated thiolene coupling, followed by deprotection using TFA (Scheme ).…”

Section: Methodsmentioning

confidence: 99%

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Effects of Nanometer Confinement on the Self-Assembly and Dynamics of Poly(γ-benzyl-l-glutamate) and Its Copolymer with Poly(isobutylene)

et al. 2022

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Poly(γ-benzyl-L-glutamate) (PBLG) and its copolymer with poly-(isobutylene) (PIB) are studied in the bulk and under nanometer confinement in pores with emphasis on the self-assembly and dynamics, respectively, with X-ray diffraction, 13 C NMR, dielectric spectroscopy, and differential scanning calorimetry. PBLG segments located within the α-helical and amorphous regions have distinct dielectric fingerprints. We have analyzed the dielectric signal from the segmental and αhelical segments to show that the α-helices are short and, furthermore, interrupted by amorphous segments. The effect of confinement is twofold: first, to speed up the segmental process and, second, to destabilize, in part, the secondary structure. The block copolymer architecture combined with confinement further destabilizes the αhelical secondary structure by introducing phase mixing. The results on the synthetic polypeptide demonstrate that both the chain configurations and the associated dynamic processes are affected when the PBLG chains are entering narrow pores. These results could pave the way for a better understanding of the behavior of more complex proteins in confined space.

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Universal properties of relaxation and diffusion in complex materials: Originating from fundamental physics with rich applications

Ngai

2023

Progress in Materials Science

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Sub-Rouse Dynamics in Poly(isobutylene) as a Function of Molar Mass

Cited by 6 publications

References 43 publications

Dynamics of Poly(cyclohexene carbonate) as a Function of Molar Mass

Dynamics of Poly(cyclohexene carbonate) as a Function of Molar Mass

Effects of Nanometer Confinement on the Self-Assembly and Dynamics of Poly(γ-benzyl-l-glutamate) and Its Copolymer with Poly(isobutylene)

Universal properties of relaxation and diffusion in complex materials: Originating from fundamental physics with rich applications

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