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The Bidirectional Shape Memory Effect of Polyurethane Photocrosslinked with Polycaprolactone and Hexamethylene Diisocyanate.

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Title: The Bidirectional Shape Memory Effect of Polyurethane Photocrosslinked with Polycaprolactone and Hexamethylene Diisocyanate.
Authors: Xu, Qiang1,2,3 (AUTHOR), Sang, Ziheng2,3 (AUTHOR), Jin, Yanmei1,3,4 (AUTHOR), Chen, Ze2,3,4 (AUTHOR), Ma, Chao1,4 (AUTHOR), Liu, Haihui2,3 (AUTHOR)
Source: Materials (1996-1944). Jun2026, Vol. 19 Issue 11, p2338. 13p.
Subjects: Polyurethanes, Polycaprolactone, Mechanical behavior of materials, Photochemical curing, Photocrosslinking, Hexamethylene diisocyanate, Shape memory polymers, Shape memory effect
Abstract: Shape memory polymers (SMPs) can undergo reversible shape transformations, yet most conventional one-way SMPs recover only a single programmed shape. Reported bidirectional SMPs frequently rely on complex chemistries or continuous external loads or tolerate pronounced losses in mechanical robustness, largely because microphase separation, crystallization and internal stress are difficult to regulate in an integrated fashion. Here, we propose a UV-programmed internal-stress-locking strategy to construct a crosslinked polyurethane (UV-SMPU) that simultaneously achieves high toughness and stable, stress-free bidirectional actuation. Using polycaprolactone (PCL) as the soft segment, hexamethylene diisocyanate (HDI) as the hard segment and triallyl isocyanurate (TAIC) as a photocrosslinker, in-situ UV curing under pre-stretch fixes a tunable three-dimensional network while "freezing" the microphase-separated morphology and pre-oriented internal stress. Covalent crosslinks stabilize PCL crystallites as reversible actuation domains, whereas hydrogen-bonded hard segments provide elastic restoring force; the coordinated regulation of crosslink density, crystallinity and locked-in internal stress enables efficient CIE/MIC-type transitions without compromising mechanical integrity. The optimized UV-SMPU (3 wt% TAIC, 10 min UV) exhibits excellent thermal stability, a rare strength–ductility balance (26.6 MPa tensile strength; ~1700% elongation) and robust bidirectional actuation, with reversible strain stabilizing at 15.73% after six cycles. This work offers a simple, scalable route to tough bidirectional SMPUs and furnishes mechanistic design principles for next-generation adaptive and soft-actuated materials. [ABSTRACT FROM AUTHOR]
Copyright of Materials (1996-1944) is the property of MDPI and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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DbLabel: Engineering Source
An: 194587249
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PubTypeId: academicJournal
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  Label: Title
  Group: Ti
  Data: The Bidirectional Shape Memory Effect of Polyurethane Photocrosslinked with Polycaprolactone and Hexamethylene Diisocyanate.
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  Data: <searchLink fieldCode="AR" term="%22Xu%2C+Qiang%22">Xu, Qiang</searchLink><relatesTo>1,2,3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Sang%2C+Ziheng%22">Sang, Ziheng</searchLink><relatesTo>2,3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Jin%2C+Yanmei%22">Jin, Yanmei</searchLink><relatesTo>1,3,4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Chen%2C+Ze%22">Chen, Ze</searchLink><relatesTo>2,3,4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Ma%2C+Chao%22">Ma, Chao</searchLink><relatesTo>1,4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Liu%2C+Haihui%22">Liu, Haihui</searchLink><relatesTo>2,3</relatesTo> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22Materials+%281996-1944%29%22">Materials (1996-1944)</searchLink>. Jun2026, Vol. 19 Issue 11, p2338. 13p.
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  Data: <searchLink fieldCode="DE" term="%22Polyurethanes%22">Polyurethanes</searchLink><br /><searchLink fieldCode="DE" term="%22Polycaprolactone%22">Polycaprolactone</searchLink><br /><searchLink fieldCode="DE" term="%22Mechanical+behavior+of+materials%22">Mechanical behavior of materials</searchLink><br /><searchLink fieldCode="DE" term="%22Photochemical+curing%22">Photochemical curing</searchLink><br /><searchLink fieldCode="DE" term="%22Photocrosslinking%22">Photocrosslinking</searchLink><br /><searchLink fieldCode="DE" term="%22Hexamethylene+diisocyanate%22">Hexamethylene diisocyanate</searchLink><br /><searchLink fieldCode="DE" term="%22Shape+memory+polymers%22">Shape memory polymers</searchLink><br /><searchLink fieldCode="DE" term="%22Shape+memory+effect%22">Shape memory effect</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Shape memory polymers (SMPs) can undergo reversible shape transformations, yet most conventional one-way SMPs recover only a single programmed shape. Reported bidirectional SMPs frequently rely on complex chemistries or continuous external loads or tolerate pronounced losses in mechanical robustness, largely because microphase separation, crystallization and internal stress are difficult to regulate in an integrated fashion. Here, we propose a UV-programmed internal-stress-locking strategy to construct a crosslinked polyurethane (UV-SMPU) that simultaneously achieves high toughness and stable, stress-free bidirectional actuation. Using polycaprolactone (PCL) as the soft segment, hexamethylene diisocyanate (HDI) as the hard segment and triallyl isocyanurate (TAIC) as a photocrosslinker, in-situ UV curing under pre-stretch fixes a tunable three-dimensional network while "freezing" the microphase-separated morphology and pre-oriented internal stress. Covalent crosslinks stabilize PCL crystallites as reversible actuation domains, whereas hydrogen-bonded hard segments provide elastic restoring force; the coordinated regulation of crosslink density, crystallinity and locked-in internal stress enables efficient CIE/MIC-type transitions without compromising mechanical integrity. The optimized UV-SMPU (3 wt% TAIC, 10 min UV) exhibits excellent thermal stability, a rare strength–ductility balance (26.6 MPa tensile strength; ~1700% elongation) and robust bidirectional actuation, with reversible strain stabilizing at 15.73% after six cycles. This work offers a simple, scalable route to tough bidirectional SMPUs and furnishes mechanistic design principles for next-generation adaptive and soft-actuated materials. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Materials (1996-1944) is the property of MDPI and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.3390/ma19112338
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 13
        StartPage: 2338
    Subjects:
      – SubjectFull: Polyurethanes
        Type: general
      – SubjectFull: Polycaprolactone
        Type: general
      – SubjectFull: Mechanical behavior of materials
        Type: general
      – SubjectFull: Photochemical curing
        Type: general
      – SubjectFull: Photocrosslinking
        Type: general
      – SubjectFull: Hexamethylene diisocyanate
        Type: general
      – SubjectFull: Shape memory polymers
        Type: general
      – SubjectFull: Shape memory effect
        Type: general
    Titles:
      – TitleFull: The Bidirectional Shape Memory Effect of Polyurethane Photocrosslinked with Polycaprolactone and Hexamethylene Diisocyanate.
        Type: main
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          Name:
            NameFull: Xu, Qiang
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            NameFull: Sang, Ziheng
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            NameFull: Jin, Yanmei
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            NameFull: Chen, Ze
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            NameFull: Ma, Chao
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            NameFull: Liu, Haihui
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          Dates:
            – D: 01
              M: 06
              Text: Jun2026
              Type: published
              Y: 2026
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            – Type: issn-print
              Value: 19961944
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              Value: 19
            – Type: issue
              Value: 11
          Titles:
            – TitleFull: Materials (1996-1944)
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