Segmented block copolymers of natural rubber and 1, 3-butanediol–toluene diisocyanate oligomers

Shape memory behaviors of trans-polyisoprene (TPI) segmented urethane copolymers were studied. Film specimens for cyclic loading tests were prepared from the polymer solution by casting, and tested at the loading temperature of 65°C. Results show that the recovery rates of the films depend on their TPI segment contents, while the fixity rate was measured to be close to 100% for each sample. The film containing 70% TPI segments was found to show a recovery rate of 85%. Two separated phases were clearly observed in the morphology of the films. The urethane segments were organized into spherical domains acting as physical cross-links during the shape memory process. The continuous phase formed by the crystalline TPI segments serves as the reversible phase responsible for fixation of the temporary shape. The tensile and dynamic thermal properties of those films were also studied.

Section: Morphology Of the Filmsmentioning

confidence: 99%

Block copolymer of trans‐polyisoprene and urethane segment: Shape memory effects

Sun

2006

“…[2][3][4][5][6] Several investigations have reported the novel type of PUs based on nonpolar macromolecular polyols such as polyisobutylene, polybutadiene, and cis-polyisoprene polyols. [7][8][9] However, in such nonpolar polyol-based PUs, there is no establishment of hydrogen bonding between soft segments and hard segments, since hydrogen bonding, as well as other interactions, is merely confined to hard segment domains. As a result, segmented PU copolymers exhibit more complete microphase separation than those containing polar polyols.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of novel polyurethanes based on 1,3‐bis(hydroxymethyl) benzimidazolin‐2‐one and 1,3‐bis(hydroxymethyl) benzimidazolin‐2‐thione hard segments

Raghu

Gadaginamath

Aminabhavi

2005

Novel polyurethanes (PUs) based on 1,3-bis(hydroxymethyl) benzimidazolin-2-one and 1,3-bis(hydroxymethyl) benzimidazolin-2-thione as hard segments with two aromatic diisocyanates, viz., 4,4Ј-diphenylmethane diisocyanate and toluene 2,4-diisocyanate, were prepared. Polymer structures were established by Fourier transform infrared and nuclear magnetic resonance spectroscopy. Morphology of the PUs was studied by differential scanning calorimetry and thermogravimetry. All PUs contain domains of crystalline and amorphous structures as indicated by X-ray diffraction experiments. Furthermore, polymers were insoluble in the majority of organic solvents and, hence, their solution characterization was not possible.

“…[14][15][16] Required stoichiometric amount of HTNR (Table I) was dissolved in chloroform (25% w/v), DBTDL catalyst, quantity of which was noted in a later section, viz., ''Copolymer synthesis'', was added and the solution was brought to reflux at 60-658C. The final stoichiometric amount of MDI in chloroform (25% w/v) was dropped into it over a period of 30 min, followed by one and a half hour reaction to endcap the HTNR.…”

Section: Synthesis Of Block Copolymersmentioning

confidence: 99%

“…[14][15][16] The two types of segments, viz., the NR and polyurethane are termed as the soft and hard segments, respectively. NR behaves as the soft segment due to its inherent flexibility.…”

Section: Copolymer Synthesismentioning

confidence: 99%

“…Recent example to this category of block copolymers are those based on liquid natural rubber and polyurethane oligomers. [14][15][16] The latter constituent is the hard phase and it has been derived from a dissymmetric diisocyanate, viz., 2,4-toluene diisocyanate on reaction with a chain extender diol such as propylene glycol, 1,3-butane diol or bisphenol A. However, it is interesting to follow the effect of symmetric diisocyanate such as MDI (4,4 0 -diphenyl methane diisocyanate) on the properties of this group of block copolymers.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Synthesis and thermal studies of block copolymers from NR and MDI‐based polyurethanes

Sukumar

Jayashree

Nair

et al. 2008

Five series of block copolymers based on natural rubber and polyurethane were prepared from hydroxyl terminated liquid natural rubber (HTNR) and polyurethane (PU) formed by the reaction of diphenyl methane-4,4 0 -diisocyanate (MDI) with a chain extender diol, viz., ethylene glycol (EG)/propylene glycol (PG)/1,4-butane diol (1,4-BDO)/1,3-butane diol (1,3-BDO)/bisphenol A (BPA), by solution polymerization. Structural characterization of the block copolymers was done by infrared (IR) analysis. Thermal studies and kinetic analysis on thermal degradation of the block copolymers were undertaken with the view of characterizing them. Energy of activation and entropy change for the degradation were determined and a probable mechanism for the solid state degradation was suggested which corresponds to a three dimensional diffusion mechanism. DSC analysis has been used for the study of microphase separation in the block copolymers. Thermal transition of the hard segment significantly varies with the extender diol which highlights the effect of extender diol structure on the chain stiffening mechanism.