Search results for "Diene"
showing 10 items of 623 documents
Myrcenol-Based Monomer for Carbanionic Polymerization: Functional Copolymers with Myrcene and Bio-Based Graft Copolymers
2020
A bio-based hydroxyl group-containing diene monomer, silyl-protected β-myrcenol (MyrOSi), is introduced to the field of carbanionic polymerization. Polymerization in cyclohexane, using sec-butyllit...
A Qualitative Analysis of Secondary Mechanisms in SEC of Polymers Through the Mean Value of the Viscosimetric Exponent
2001
Abstract Size exclusion chromatography (SEC) universal calibration curves for poly(dimethylsiloxane), polybutadiene and poly(2-vinylpyridine) samples have been obtained in columns packed with cross-linked polystyrene gel using cyclohexane, toluene, benzene, dioxane and tetrahydrofuran as eluents at 25°C. The eluents exhibit different thermodynamic quality for the polymeric solutes and for the gel matrix which is reflected in the values of their Mark-Houwink-Sakurada exponents a. The plots of log(hydrodynamic volume) versus retention volume for the polymeric solutes in different eluents are displaced to higher retention volumes than that of THF-polybutadiene (ideal SEC), evidencing the exist…
Multi-olefin containing polyethers and triazolinediones: a powerful alliance
2019
Multi-functional polyethers with ene or diene moieties were prepared via the polymerisation of tailored functional glycidyl ether monomers to create a platform for click chemistry with triazolinediones (TADs). Specifically, two novel monomers (i) 2,4-hexadien-1-yl glycidyl ether (HDEGE) and (ii) citronellyl glycidyl ether (CitroGE), designed to undergo a Diels–Alder or Alder–Ene reaction with TADs, respectively, were synthesized and subsequently transformed into a variety of tailored polyethers, either via the monomer activated method or anionic ring opening polymerisation. Multi-functional copolymers of HDEGE with ethylene oxide, propylene oxide and ethoxy ethyl glycidyl ether as well as A…
Synthesis and properties of amphiphilic “dumbbell”-shaped grafted block copolymers, 1. Anionic synthesis via a polyfunctional initiator
1994
Two poly(ethylene oxide) stars linked by a long polystyrene chain represent a novel amphiphilic architecture (dumbbell), which is available by anionic grafting of ethylene oxide from a hydroxylated polybutadiene-block-polystyrene-block-polybutadiene triblock copolymer. The short butadiene end-blocks (DPB = 36) of a BSB triblock copolymer with a long styrene middle block (DPS = 650) was first modified by hydroboration and oxidation. A multifunctional alkoxide initiator is thus prepared by titration of the hydroxyl groups of the “polybutadiene” end-block with cumylpotassium. Gelation and precipitation of the polyfunctional initiator in THF could be avoided by complexing the cation (K+) with a…
Synthesis of SBC, SC and BC block copolymers based on polystyrene (S), polybutadiene (B) and a crystallizable poly(ɛ-caprolactone) (C) block
1996
The sequential anionic polymerization of polystyrene-block-polybutadiene-block-poly(e-caprolactone) (SBC) triblock copolymers as well as polystyrene-block-poly(e-caprolactone) (SC) and polybutadiene-block-poly(e-caprolactone) (BC) diblock copolymers was achieved in benzene. To initiate the polymerization of the highly reactive e-caprolactone, the nucleophilicity of the carbanion has to be reduced. For this purpose 1,1-diphenylethylene (DPE) was used. To avoid inter- and intramolecular transesterification reactions of the growing caprolactone block, the reaction time of this monomer in the block copolymers was strictly controlled. The reaction between polybutadienyl anions and DPE is too slo…
Joining Two Natural Motifs: Catechol-Containing Poly(phosphoester)s.
2017
Numerous catechol-containing polymers, including biodegradable polymers, are currently heavily discussed for modern biomaterials. However, there is no report combining poly(phosphoester)s (PPEs) with catechols. Adhesive PPEs have been prepared via acyclic diene metathesis polymerization. A novel acetal-protected catechol phosphate monomer was homo- and copolymerized with phosphoester comonomers with molecular weights up to 42000 g/mol. Quantitative release of the catechols was achieved by careful hydrolysis of the acetal groups without backbone degradation. Degradation of the PPEs under basic conditions revealed complete and statistical degradation of the phosphotri- to phosphodiesters. In …
Structure of isotactic polypropylene/ hydrogenated oligo(cyclopentadiene) blends: 1. Polypropylene-rich blends
1998
Blends of isotactic polypropylene (iPP) and hydrogenated oligo(cyclopentadiene) (HOCP) containing 30% or less HOCP have been studied by small-angle X-ray scattering in the temperature range 25 to 160°C. The structure of blends has been analysed in terms of a pseudo two-phase model consisting of stacks of lamellae whose thickness is a function of temperature and composition. Structural parameters of the model have been derived and their temperature and composition dependences have been interpreted in the light of existing theories.
Photo-Stability Improvement of Polystyrene-block-Polybutadiene-block-Polystyrene through Carbon Nanotubes
2015
The photo-oxidation stability of Polystyrene-Polybutadiene-Polystyrene (SBS) based nanocomposites containing bare multi-walled carbon nanotubes (CNTs) and carbon nanotubes bearing hydroxyl functional groups (CNTs-OH) in comparison to that of pristine SBS has been widely investigated. The photo-oxidation of pristine SBS occurs through crosslinking reactions and oxidized species formation and both these processes begin at early stage of exposure. The formation of crosslinking, formerly in polybutadiene phase, assessed by spectroscopical (FTIR), mechanical, dynamic mechanical and rheological analysis, leads to occurrence of internal mechanical stresses in the solid state and the SBS samples be…
Taisnīguma atjaunošana Valsts probācijas dienesta organizētā izlīgumā
2018
Izlīgums ir brīvprātīga cietušā un likumpārkāpēja tikšanās un iesaistīšanās sarunā ar starpnieka palīdzību, lai kopīgi runātu par notikušo un meklētu abām pusēm pieņemamu un savstarpēji taisnīgu risinājumu. Izlīguma pamatā tiek izmantota taisnīguma atjaunošanas pieeja noziedzīga nodarījuma rezultātā radušos seku mazināšanā. Bakalaura darba mērķis ir analizēt, kā un cik efektīvi Valsts probācijas dienestā tiek organizēts izlīgums un izlīguma sanāksme. Darba uzdevumi ir analizēt Latvijas regulējumu, statistikas datus, kā arī tiesību doktrīnā paustās atziņas. Pētījuma rezultātā autore gūst ieskatu Valsts probācijas dienesta rīkota izlīguma procedūrā un konstatē atsevišķus problēmjautājumus. Da…
Kriminālsoda- piespiedu darbs- izpildes organizēšanas prakses analīze un ieteikumu izstrāde tās uzlabošanai
2016
Maģistra darba temats „Kriminālsoda – piespiedu darbs – izpildes organizēšanas prakses analīze un ieteikumu izstrāde tās uzlabošanai”. Darba mērķis - noskaidrot sabiedrībā pastāvošos viedokļus par piespiedu darba efektivitāti, salīdzinot ar citiem kriminālsodu veidiem, pētīt, analizēt statistikas datus un piespiedu darba piemērošanas praksi. Mērķa sasniegšanai tika izvirzīti šādi uzdevumi: •analizēt juridisko literatūru, kas saistīta ar piespiedu darbu; •noskaidrot piespiedu darba jēdzienu, piemērošanas un izpildes kārtību; •pētīt piespiedu darba pozitīvas puses un iespējamās problēmas; •noskaidrot galvenos priekšstatus par piespiedu darba un citu kriminālsodu veidu ietekmi uz likumpārkāpēj…