Impact of dynamic covalent chemistry and precise linker length on crystallization kinetics and morphology in ethylene vitrimers

Soft Matter ◽  
2022 ◽  
Author(s):  
Bhaskar Soman ◽  
Yoo Kyung Go ◽  
Chengtian Shen ◽  
Cecilia Leal ◽  
Christopher M. Evans
Keyword(s):  
Crystal Structure ◽  
Melting Temperature ◽  
Crystallization Kinetics ◽  
Polymer Networks ◽  
Exchange Reactions ◽  
Dynamic Covalent Chemistry ◽  
Linker Length

Vitrimers, dynamic polymer networks with topology conserving exchange reactions, can lead to unusual evolution of the melting temperature and crystal structure of ethylene networks.

Synthese, Struktur und thermisches Verhalten von Thiophosphorsäuretriamid SP(NH2)3 [1] / Synthesis, Structure, and Thermal Behaviour of Phosphorothionic Triamide SP(ΝΗ2)3 [1]

1989 ◽  
Vol 44 (8) ◽  
pp. 942-945 ◽  
Author(s):  
Wolfgang Schnick
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Thermal Properties ◽  
Single Crystal ◽  
Melting Temperature ◽  
Intermolecular Hydrogen Bonding ◽  
X Ray ◽  
Hydrogen Bonding Interactions ◽  
Ray Methods ◽  
Single Bonds

Phosphorothionic triamide SP(NH2)3 is obtained by slow addition of SPCl3 dissolved in dry CH2Cl2 to a satured solution of NH3 in CH2Cl2 at —50°C. Ammonium chloride is removed from the resulting precipitate by treatment with HNEt2 followed by extraction with CH2Cl2. Coarse crystalline SP(NH2)3 is obtained after recrystallization from dry methanol. The crystal structure of SP(NH2)3 has been determined by single crystal X-ray methods (Pbca; a = 922.3(1), b = 953.8(1), c = 1058.4(2) pm, Z = 8). In the crystals the molecules show non-crystallographic point symmetry C8. The P—S bond (195.4(1) pm) is slightly longer than in SPCl3. From P—N bond lengths of about 166 pm a significant electrostatic strengthening of the P—N single bonds is assumed. Weak intermolecular hydrogen bonding interactions (N —H · · · N ≥ 329.5 pm; N — H · · · S ≥ 348.3 pm) are observed.Investigation of thermal properties shows a melting temperature of 115°C for SP(NH2)3. According to combined DTA/TG and MS investigations above this temperature the compound decomposes by evolution of H2S and NH3 to yield amorphous phosphorus(V)nitride.

Crystallization in Stretched Polymer Networks. I. trans-Polychloroprene

1967 ◽  
Vol 40 (4) ◽  
pp. 1071-1083 ◽  
Author(s):  
A. N. Gent
Keyword(s):  
Melting Temperature ◽  
Polymer Networks ◽  
Crystal Form ◽  
Simple Extension ◽  
Theoretical Treatment ◽  
Nucleation Kinetics ◽  
Segmental Mobility ◽  
Melting Temperatures ◽  
Direct Measurements ◽  
Stress Changes

Abstract Changes in tensile stress afford a simple means of studying the rates of crystallization and the melting temperatures in crosslinked polymers subjected to simple extension. The form and magnitude of the stress changes in networks of trans-polychloroprene are closely similar to those observed for cis-1:4-polyisoprene and cis-l:4-polybutadiene networks. They are in accord with the formation of oriented crystallites and incompatible with folded chain crystallization at extensions as low as 15 per cent. It seems likely that the present networks do not crystallize by chain folding even in the unstretched state. The large increases in rate of crystallization with extension are approximately accounted for by corresponding increases in the equilibrium melting temperature. Direct measurements of the melting temperature show similar rises with extension. The rise in melting temperature is in good agreement with Flory's theoretical treatment of oriented crystallization at extension ratios of three and higher (when the crystallite orientation is complete) for three networks having different degrees of crosslinking. When referred to a constant segmental mobility, namely, that obtaining at Tg+50° C, the rates of crystallization at various extensions obey a common dependence upon the degree of supercooling. This relation is in fair accord with theories of nucleation kinetics, except at the lowest temperatures where there is some indication of the appearance of a new crystal form.

scholarly journals Dynamic covalent chemistry in polymer networks: a mechanistic perspective

2019 ◽  
Vol 10 (45) ◽  
pp. 6091-6108 ◽  
Author(s):  
Johan M. Winne ◽  
Ludwik Leibler ◽  
Filip E. Du Prez
Keyword(s):  
Physicochemical Properties ◽  
Reaction Mechanisms ◽  
Polymer Networks ◽  
Molecular Network ◽  
Polymer Materials ◽  
Dynamic Covalent Chemistry ◽  
Selection Of

A selection of dynamic chemistries is highlighted, with a focus on the reaction mechanisms of molecular network rearrangements, and on how mechanistic profiles can be related to the mechanical and physicochemical properties of polymer materials.

scholarly journals Cross-Linked Polythiomethacrylate Esters Based on Naphthalene—Synthesis, Properties and Reprocessing

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3021
Author(s):  
Karolina Fila ◽  
Beata Podkościelna ◽  
Maciej Podgórski
Keyword(s):  
Polymer Networks ◽  
Polymeric Materials ◽  
Exchange Reactions ◽  
Scanning Calorimetry ◽  
Swelling Properties ◽  
Ene Reaction ◽  
Synthesis Properties ◽  
Double Bond Conversion ◽  
Swelling Studies ◽  
Synthesized Materials

Two structurally different aromatic dithioesters were synthesized from two dithiols and methacryloyl chloride. The polymer networks based on methyl methacrylate and/or styrene and the new dimethacrylates were subsequently prepared. The polymerization yields of copolymers were in the range of 95–99%. The thermal and mechanical properties of the copolymers were determined by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TG/DTG), and Shore D hardness. The addition of dithioesters—1,5-NAF-S-Met (or 1,4(1,5)-NAF-CH2S-Met) (from 0.5% to 5%) to MMA- or ST-based polymers results in lowering the glass transition temperature (Tg) by about 8 °C. The thioester-containing polymers based on MMA exhibit lower thermal stability than those with ST. The polythioesters are stable up to 250 °C. The UV/vis spectra and refractive indexes of prepared liquid compositions were also measured. The 1,5-NAF-S-Met (and 1,4(1,5)-NAF-CH2S-Met) improved the refractive index values of ST and MMA compositions. The double bond conversion was also determined for all synthesized materials. The swelling studies of polymers with 20% addition of thioester crosslinkers were investigated. For all polymeric materials with 20% addition of thioesters, depolymerization of the network was carried out by thiol-thioester exchange. The depolymerization products were re-reacted in a thiol-ene reaction with 2-hydroxyethyl methacrylate by thermal initiation. The thiol-ene procedure enabled reprocessing of starting polymers and obtaining new materials characterized by distinctly different thermal, mechanical, and swelling properties. The thiol-ene materials exhibit a lower Shore hardness in the range of 20–50 °Sh, as well as decreased Tg values when compared to starting copolymers. Due to these possible exchange reactions, one can facilely manipulate the properties of the polymers which could lead to the manufacturing of the new products with the desired features. Degradation of the cross-linked structure and recycling of copolymers were also discussed.

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