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The graft polymerization of tert-butyl acrylate (TBA) onto polyurethane (PU) was conducted to prepare a series of samples that was compared to a control series comprising a physical mixture of poly(TBA) and PU. Maximum tensile stress sharply increased because of chemical cross-linking via poly(TBA), whereas tensile breaking strain slightly diminished by the grafted poly(TBA). Percent shape recovery at 10°C rapidly increased by the additional grafting of poly(TBA), whereas control series decreased with increases in TBA monomer content. Chemical cross-linking from the grafted poly(TBA) was responsible for the enhancement of shape recovery. Low-temperature flexibility tests from −35°C demonstrated that a proper composition of grafted poly(TBA) could enhance the flexibility of PU below 0°C. Overall, the grafted poly(TBA) greatly stepped up the maximum tensile stress, recovery capability to original form, and flexibility of PU at very low temperature.

A pH indicator (Bromocresol Green, Bromocresol Purple, or Thymol Blue) is grafted onto polyurethane (PU) using 2,2-dimethylolpropanoic acid (DMPA) to enhance water compatibility. The indicator-grafted, water-compatible PU is analysed for soft-segment thermal, tensile, and shape recovery properties, fast colour change depending on various pH conditions, and low-temperature flexibility. The PU surface becomes water compatible as DMPA content increases, and the characteristic UV-vis absorbance is observed for each grafted indicator. The PU series exhibits a sharp increase in tensile stress and crosslink density at low DMPA content, but a decrease with increased DMPA content. The glass transition temperature increases significantly with increased DMPA content. Shape recovery remains high, but shape retention sharply decreases after an indicator is grafted. The grafting of pH indicator onto PU improves the low-temperature flexibility and imparts an immediate colour change according to the solution pH and grafted indicator.

Polycaprolactam or polycaprolactone was graft-polymerized onto polyurethane (PU) to control the water vapor permeation and improve the tensile strength of PU. The tensile strength of the PU sharply increased with the grafting of polycaprolactam or polycaprolactone, without a decrease in the tensile strain. The soft segment melting properties did not significantly change with the increase in the lactam or lactone content. The shape recovery and shape retention of the PU series remained high after the grafting. The water vapor permeability (WVP) was reduced by the grafting of the polycaprolactam, whereas the WVP was increased by the grafting of polycaprolactone.

Epichlorohydrin (ECH) was used as a cross-linking agent for a series of polyurethanes (PU series). The spectroscopic, thermal, tensile, shape memory, low-temperature flexibility, and water vapor permeability properties of these PUs were compared with those of a control polyurethane series (CPU series) without ECH cross-linking. In the thermal test, the soft segment crystallization of the PU series disappeared as the ECH cross-linking increased. The glass transition temperature (Tg) of the PU and CPU series slightly increased with the increase in ECH content. The tensile strength of the PU series sharply increased at a critical ECH content, whereas that of the CPU series did not. The breaking strain of the PU and CPU series remained the same with the increase in ECH content. The shape recovery of the PU series remained above 90% at 45°C but increased moderately with the increase in ECH content at 0°C. Finally, the PU series with ECH cross-linking demonstrated better low-temperature flexibility and lower water vapor permeability than the unmodified PU.

Polyacrylonitrile (PAN) or poly(methyl methacrylate) (PMMA) was graft-polymerized onto polyurethane (PU) to form the urethane-acrylate polymers grafted with PAN (UA series) or PMMA (UM series). With an increase in the acryl content, the T m, ΔH m , and T g did not significantly change for the UA and UM series. The tensile strengths of the UA and UM series increased with the acryl content, whereas those of the control PUs did not. The breaking strain of the UA and UM series, and control PUs remained the same with the increase in the acryl content. The shape recovery and shape retention of the UA and UM series remained high after four repeated tests. The UA and UM series demonstrated better low-temperature flexibility and water permeability than the unmodified PU.

End groups with different structures were grafted to polyurethane (PU) using poly(dimethylsiloxane) (PDMS) as a spacer. The low-temperature toughness of the PUs was tested at −30°C, and the structure selectivities of the end groups for low-temperature toughness were compared. The PDMS functioned as a flexible linker that connected the end groups to the PUs. The tensile strength of the PU generally improved despite the grafting of PDMS and end groups. The conventional shape recovery ratio at 45°C remained greater than 90%, regardless of the content and structure of PDMS and the end group. The PU that contained an adamantyl group (cubic) or a naphthyl group (planar rectangle) showed instant recovery, even at −30°C, but the PU that contained a phenyl (planar square) or phenoxyphenyl (bent squares) group required warming to 0°C for a similar degree of recovery but showed improvement over a linear PU without any end group. The characteristic structure of the end group was responsible for the selective low-temperature toughness. The low-temperature toughness results and the thermal and mechanical properties of the PUs are discussed. POLYM. ENG. SCI., 55:1931–1940, 2015. © 2014 Society of Plastics Engineers

Photoluminescent dyes (aminofluorene, naphthalimide, naphtholbenzein, or phenosafranine) were grafted to polyurethane using an allophanate linkage. The photoluminescence properties and the shape recovery effects of polyurethane samples were investigated. The polyurethane was composed of 4,4′-methylenebis(phenylisocyanate), poly(tetramethyleneglycol), and 1,4-butanediol. The dyes were linked through an extra 4,4′-methylenebis(phenylisocyanate) and the carbamate moiety of the polyurethane chains. Polyurethanes with various dye contents were characterised, and the shape recovery and photoluminescence properties were compared. In the case of the tensile mechanical properties, the highest maximum stress was 56 MPa, and the strain remained > 1500% for the entire series. The shape recovery improved as the test cycle was repeated, with up to 100% recovery being achieved, but shape retention decreased as the dye content increased. Finally, the photoluminescence of the polyurethanes was demonstrated by a luminescent light-emission test, together with pH indication capability and the preparation of non-woven fibre using the electrospinning method.

Polyurethane (PU) with a diphenylamino side group is tested for low temperature flexibility at −30°C and compared with a linear PU without the diphenylamino side group. The PU is composed of 4,4′-methylenebis(phenylisocyanate) (MDI), poly(tetramethyleneglycol) (PTMG), 1,4-butanediol (BD), and the diphenylamino group that is grafted to PU chains by a second MDI. The mechanical and shape memory properties of these two types of PU, which differ in the PTMG and the diphenylamino group content, are compared. In the best case, a 306% increase in the maximum stress compared with the linear polymer is attained with a little decrease in the strain. Shape recovery at 45°C increases to 94% and remains ∼90% after four cyclic tests. Low temperature flexibility can be improved by increasing the diphenylamino content. The PU with a diphenylamino side group demonstrates the low temperature flexibility at −30°C, whereas the linear PU must be warmed to room temperature to attain the same degree of flexibility. The exceptional low temperature flexibility is analyzed and is discussed together with the experimental data. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Malic acid, a molecule containing two carboxyl groups per molecule, was grafted to polyurethane (PU) through a carbamate group. The polymer was transformed to the anionic carboxylate form to observe the impact on the tensile strength and shape recovery of the PU. The electrostatic repulsion of the carboxylate reduced the molecular interactions between PUs, a result that was designed to improve the shape recovery at sub-zero temperatures while maintaining high and reproducible tensile strength and shape recovery at ambient temperatures. The grafted carboxyl group was quantitatively determined by acid–base titration, and the change in the molecular interactions was confirmed via IR spectroscopy and differential scanning calorimetry. The viscosity experienced an unusual increase with increasing carboxylate content due to the covalent crosslinking caused by the grafting reagent. Shape recovery and retention were reproducible over repeated shape memory tests. Finally, the shape recovery behavior of each PU was compared at temperatures between −30 and 10°C. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Lateral flexible linking of shape memory polyurethane (SMPU) by a polyethyleneglycol (PEG) linker through the allophanate linking method was studied, while adjusting the soft segment content and PEG length. The SMPU was composed of 4,4′-methylenebis(phenylisocyanate) (MDI), poly(tetramethyleneglycol) (PTMG), 1,4-butanediol (BD), and PEG-200 as a linker. A second MDI was used to connect the carbamate group of the SMPU chain and PEG. The impact of soft segment content and PEG length on the mechanical properties and shape recovery of two series of SMPU were compared. In the best case, a 545% increase in maximum stress compared to a linear polymer was attained. The flexibly crosslinked SMPUs behave similarly to natural rubber in their stress–strain curve, but their tensile mechanical properties surpassed those of natural rubber. Shape recovery went up to 96%, which is among the best SMPUs tested so far, and shape recovery remained above 90% after four cyclic tests. The extraordinary shape memory results are analyzed and discussed together with DSC and IR data. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Shape memory polyurethane (SMPU), flexibly crosslinked via a polyethyleneglycol (PEG) spacer attached to its side through an allophanate group, was tested for shape memory and compared with a linear SMPU. The new SMPU was composed of 4,4′-methylenebis(phenylisocyanate) (MDI), poly(tetramethyleneglycol) (PTMG-2000), and 1,4-butanediol (BD), and included polyethyleneglycol (PEG-200) as a spacer. A second MDI, linked to the carbamate group of the first MDI, served as the connecting point for the PEG-200. Two types of SMPU, differing according to their soft segment (PTMG-2000) and linker (PEG-200) contents, were compared in mechanical and shape memory properties. In the best case, a 780% increase in maximum stress was attained without any sacrifice in strain for the new material compared with the linear polymer. In particular, the stress–strain curve showed that the PEG-crosslinked SMPU had superior tensile mechanical properties. Its shape recovery was as high as 99%, which is the best value we have measured for an SMPU. After four cyclic tests, shape recovery remained greater than 95%. Shape retention of the best SMPU remained above 93% even after four cyclic tests. Here, results demonstrating the extraordinary shape memory properties of these types of SMPU, together with differential scanning calorimetry (DSC) and infrared spectroscopy data, are analyzed and discussed. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers

Celite, a porous inorganic material with enormous surface area and hydroxyl groups on the surface, was used as a cross-linker of polyurethane (PU) copolymer chains to improve its shape memory and mechanical properties. PU copolymers with different Celite contents were prepared and characterized by IR, DSC, and universal testing machine. The glass transition temperature of PU copolymers was maintained around 20°C independent of Celite content. The shape memory and mechanical properties were dependent on when Celite was added during the polymerization reaction. The reaction in which Celite was added at the middle stage of polymerization showed the best shape memory and mechanical properties. The best shape recovery of PU was found at 0.3 wt % Celite and increased to 97% even after the third cycle. Likewise, the shape retention also maintained a remarkable 86% after three cycles. The reasons underlining the high shape recovery and shape retention by adopting Celite as a cross-linker are discussed in this article. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

A series of polyurethane (PU) polymers cross-linked laterally by pentaerythritol and polyethyleneglycol (PEG) spacers were compared with linear PU. The PU was composed of 4,4′-methylenebis(phenylisocyanate) (MDI), poly(tetramethyleneglycol), 1,4-butanediol (BD), pentaerythritol, and PEG-200 as a spacer. PEG-200 connected the pentaerythritol hydroxyl groups of two PU chains with MDI as a connecting agent. The phase separation between hard and soft segments was disrupted by the PEG crosslinking, and Tm did not change with an increase in cross-linking content. Instead, the cross-link density increased with an increase of pentaerythritol content. A significant increase in maximum stress compared with linear PU was attained, together with an increase in strain. The combination of both pentaerythritol and PEG-200 in the PU resulted in the improvement of both stress and strain, unlike in the conventional cross-linking method. The shape recovery increased to 90% and did not decrease after three test cycles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Poly(ethylene terephthalate) (PET) and poly (ethylene glycol) (PEG) copolymers crosslinked with glucose as a crosslinker are prepared to improve their mechanical and shape memory properties compared to the one without crosslinking. Composition of PEG and glucose is varied to search for the one with the best mechanical and shape memory properties. The highest shape recovery rate is found in the copolymer composed of 25 mol % PEG-200 and 2.0 mol % glucose. The result that crosslinking by glucose improves the shape recovery rate and supports the high shape recovery rate under the repetitive cyclic test conditions, compared to the one without crosslinking, will be discussed in the points of the structure and shape memory mechanism. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Nanocomposites from polyurethane (PU) and montmorillonite (MMT) were prepared under melt- mixing condition, by a twin screw extruder along with a compatibilizer to enhance dispersion of MMT. MMT used in this study was Cloisite 25A (modified with dimethyl hydrogenated tallow 2-ethylhexyl ammonium) or Cloisite 30B (modified with methyl tallow bis-2-hydroxyethyl ammonium). Maleic anhydride grafted polypropylene (MAPP) was used as the compatibilizer. XRD and TEM analysis demonstrated that melt mixing by a twin-screw extruder was effective in dispersing MMT through the PU matrix. The PU/Cloisite 30B composite exhibited better interlayer separation than the PU/Cloiste 25A composite. Nanoparticle dispersion was the best at 1 wt % of MMT and improved with compatibilizer content for both compo- sites. Properties of the composites such as complex viscos- ity and storage modulus were higher than that of a pure PU matrix and increased with the increase in MMT con- tent, but decreased with the increase in compatibilizer con- tent. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 106: 712- 721, 2007

The arrangements, whether block or random type, of the soft segments of polyurethane block copolymers prepared with MDI and two kinds of poly(tetramethylene glycol) (PTMG; MW of 1000 or 2000) in various ratios were compared for possible effects on the physical properties of the copolymers. A long soft segment, PTMG-2000, was superior in all mechanical properties (strain, stress, and modulus) because a long chain length could provide more motional freedom than a short one (PTMG-1000) could and therefore was helpful in forming strong interchain attractions among hard segments. Inclusion of more PTMG-2000 led to a lower Tg and a peak shift in infrared spectra. The arrangement of two soft segments in a block-type copolymer, a key finding in this study, was controlled by separately synthesizing two prepolymers, each with a different chain length, and connecting two prepolymers in a second step. Random-type copolymers prepared for purposes of comparison were allowed to react with two PTMGs in one step. Two types of copolymers were compared, and the reason for the differences in the shape memory property are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1435–1441, 2007

Water vapor permeable fabrics were prepared by coating shape-memory polyurethane (PU), which was synthesized from poly(tetramethylene glycol), 4,4'-methylene bis(phenylisocyanate), and 1,4-butanediol, onto polyester woven fabrics. Water vapor permeability and mechanical properties were investigated as a function of PU hard-segment content or polymer concentration of the coating solution. Water vapor permeability of PU-coated fabrics decreased dramatically with increased concentration of coating solution, whereas only a slight change was observed with the control of PU hard-segment content. The coated fabric showed the clear appearance of a nonporous PU surface according to SEM measurements. Attainment of high water permeability in PU-coated fabrics is considered to arise from the smart permeability characteristics of PU. Mechanical properties of coated fabrics, although there was some variation depending on the concentration of coating solution, were primarily affected by PU hard-segment content. Fabrics coated with PU hard-segment content of 40% showed the lowest breaking stress and modulus as well as the highest breaking elongation, which could be interpreted in terms of the dependency of mechanical properties of coated fabrics on PU hard-segment content and the yarn mobility arising from a difference in penetrating degree of coating solution into the fabric.

High-performance shape-memory polyurethane block copolymers, prepared with two types of poly(tetramethylene glycol) (PTMG) used as soft segments, were investigated for their mechanical properties. Copolymers with a random or block soft-segment arrangement had higher stresses at break and elongations at break than those with only one kind of PTMG. Random copolymers with fewer interchain interactions showed higher elongation than block copolymers. All the copolymers had shape-recovery ratios higher than 80%. In dynamic mechanical testing, the glass-transition behavior clearly depended on the soft-segment arrangement: random copolymers had only one glass-transition peak, whereas block copolymers showed two separate glass-transition peaks. Overall, the control of the soft-segment arrangement plays a vital role in the development of high-performance shape-memory polyurethane. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2410–2415, 2004

Poly(ethylene terephthalate) (PET) and poly(ethylene glycol) (PEG) copolymers crosslinked with glycerol and sulfoisophthalate (SP) were prepared to investigate the feasibility of fabricating smart vibration-controlling composite laminate. The composition of glycerol and SP was varied to get a copolymer with the best mechanical and shape memory properties. The highest shape recovery was observed for the copolymer with 2.5 mol % of glycerol and 2.5 mol % of SP. With the high shape-recovery copolymer in hand, sandwich-type copolymer composites were made with epoxy beam laminate, and the copolymer composite, in the best case, showed improved impact strength (3.5 times) and damping effect (2.6 times) compared to epoxy laminate beam alone. The sandwich-type epoxy composite, together with the advantage of control of glass transition temperature by PET, PEG, or the additives, can be applied to structural composite material requiring vibration control. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 308–316, 2004

To make smart vibration-controlling composite laminate, a few poly(ethylene terephthalate) (PET) and poly(ethylene glycol) (PEG) copolymers with shape memory ability were prepared. After selecting the best composition of PET–PEG copolymer in mechanical properties, a crosslinking agent such as glycerine, sorbitol, or maleic anhydride (MA) was included for crosslinked copolymer, followed by analysis of its effect on mechanical, shape memory, and damping properties. The highest shape recovery was observed for copolymer with 2.5 mol % of glycerine, and the best damping effect indicating vibration control ability was from copolymer with 2.5 mol % of sorbitol. With the optimum copolymers in hand, sandwich-structured epoxy beam composites fabricated from an epoxy beam laminate and crosslinked PET–PEG copolymer showed that impact strength increased from 1.9 to 3.7 times depending on the type of copolymer, and damping effect also increased as much as 23 times for the best case compared to epoxy laminate beam alone. The resultant sandwich-structured epoxy beam composite can be utilized as structural composite material with vibration control ability, and its glass transition temperature can be controlled by adjustment of PET, PEG, or crosslinking agent composition. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3141–3149, 2003

We compared two series of benzimidazole (BI)-grafted polyurethane (PU), one of which was water-compatible, to compare their antifungal activities. The water-compatible PU series had an additional 2,2-bis(hydroxymethyl)propanoic acid group in the PU backbone. The water-compatible PU series had a lower crosslinking density and tensile strength compared to the other PU series with increasing BI content. Although ordinary PU did not suppress fungal growth (Chaetomium globosum), the water-compatible PU completely suppressed the growth even though it contained half as many BI groups. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41676.

Dimethyl terephthalate (DMT) and ethylene glycol (EG) were used for the preparation of poly(ethylene terephthalate) (PET), and poly(ethylene glycol) (PEG) was added as a soft segment to prepare a PET–PEG copolymer with a shape-memory function. MWs of the PEG used were 200, 400, 600, and 1000 g/mol, and various molar ratios of EG and PEG were tried. Their tensile and shape-memory properties were compared at various points. The glass-transition and melting temperatures of PET–PEG copolymers decreased with increasing PEG molecular weight and content. A tensile test showed that the most ideal mechanical properties were obtained when the molar ratio of EG and PEG was set to 80:20 with 200 g/mol of PEG. The shape memory of the copolymer with maleic anhydride (MAH) as a crosslinking agent was also tested in terms of shape retention and shape recovery rate. The amount of MAH added was between 0.5 and 2.5 mol % with respect to DMT, and tensile properties and shape retention and recovery rate generally improved with increasing MAH. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 27–37, 2002

Titanium dioxide and nylon covalently supported iodosobenzoate reagents 11 and 19 have been prepared. Both 11 and 19 are good catalysts for the cleavage of p-nitrophenyl diphenyl phosphate (PNPDPP) under heterogeneous aqueous conditions at pH 8. The kinetics of the cleavage reactions have been characterized in the presence of excess substrate (turnover conditions), and in the presence of dilute cetyltrimethylammonium chloride, which enhances both PNPDPP cleavage and catalyst turnover