Table Of ContentAdvances in Polymer Science 263
Oguz Okay Editor
Polymeric
Cryogels
Macroporous Gels with Remarkable
Properties
263
Advances in Polymer Science
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Oguz Okay
Editor
Polymeric Cryogels
Macroporous Gels with Remarkable
Properties
With contributions by
(cid:1) (cid:1) (cid:1)
F. Auriemma A.D. Bannerman C. De Rosa
(cid:1) (cid:1) (cid:1) (cid:1)
R. Di Girolamo V.I. Lozinsky H. Mak B. Mattiasson
(cid:1) (cid:1) (cid:1) (cid:1)
O. Okay P.D. Petrov O.A. Shlyakhtin C.B. Tsvetanov
(cid:1)
W. Wan L. Yang
Editor
OguzOkay
DepartmentofChemistry
IstanbulTechnicalUniversity
Istanbul,Turkey
ISSN0065-3195 ISSN1436-5030(electronic)
ISBN978-3-319-05845-0 ISBN978-3-319-05846-7(eBook)
DOI10.1007/978-3-319-05846-7
SpringerChamHeidelbergNewYorkDordrechtLondon
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Preface
Cryogelationisasimplestrategythatallowsthepreparationofmacroporousgels,
so-calledcryogels,ofhightoughnessandsuperfastresponsivity.Theterm“cryogel”
wasmentionedintheliteratureforthefirsttimein1984byVladimirI.Lozinskyto
designatepolymericgelsformed infrozenmedia. Cryogelshave attractedintense
attention in the last 10 years due to their extraordinary properties, which have
resulted in numerous biotechnological and biomedical applications. The present
volumeentitledPolymericCryogels:MacroporousGelswithRemarkableProper-
tiesisintendedtoreviewtheprinciplesofcryotropicgelationprocessesaswellas
theadvancesmadeduringthepasttwodecadesinthepreparationandapplicationof
cryogels based on both synthetic and natural polymers. It is my great pleasure to
haveVladimirI.Lozinskyasoneoftheauthorsofthisvolume.Iverymuchenjoyed
discussingmanyaspectsofcryogelsandsomesecretsofcryogelationprocesseswith
him,bothinIstanbulandatcryogenictemperaturesinMoscow(Fig.1).
The history of polymeric cryogels and mechanisms of their formation are
reviewed in the first chapter. Chapters “Basic Principles of Cryotropic Gelation”
and “Synthesis and Structure-Property Relationships of Cryogels” cover the basic
principlesofcryotropicgelation,the synthesis–structure–propertyrelationshipsof
cryogels,andsomeoftheirnovelapplications.Aqueouspoly(vinylalcohol)(PVA)
solutionsformphysicalgelsbycryogenictreatments,whichareofgreatinterestdue
totheiroutstandingproperties.FormationofPVAcryogelsundervariousconditions
isdiscussedindetailinchapters“ABriefHistoryofPolymericCryogels,”“Basic
Principles of Cryotropic Gelation,” “Kinetic Analysis of Cryotropic Gelation of
Poly(vinylalcohol)/watersolutionsbySmall-AngleNeutronScattering,”and“Poly
(vinyl alcohol) Cryogels for Biomedical Applications.” The structure of PVA
cryogels and the principal processes taking place during their formation are
discussed in chapter “Kinetic Analysis of Cryotropic Gelation of Poly(vinyl alco-
hol)/watersolutionsbySmall-AngleNeutronScattering”.Aneffectivemethodfor
thesynthesisofpolymercryogelsistheinitiationofcryogelationreactionsusingUV
irradiation, which is reviewed in chapter “Cryogels via UV Irradiation”.
Chapter“InorganicCryogels”coversrecentadvancesininorganiccryogels.Ihave
tomentionthat,althoughtheterm“inorganiccryogel”hasbeenusedasthegeneric
v
vi Preface
Fig.1 Lowtemperatureis
aprerequisiteforobtaining
cryogels.O.Okay(left)and
V.I.Lozinsky(right)
discussingthecontentof
thisvolumeat(cid:3)23(cid:4)Cin
Moscow(1February2014)
name for freeze-dried products of inorganic gels, precipitates, and colloidal solu-
tions, it is more correct to call such freeze-dried products “cryostructurates” or
“cryotexturates” rather than cryogels. However, as the term “cryogel” is most
commonly used for inorganic materials obtained by free-drying, it will also be
usedinchapter“InorganicCryogels”tobeconsistentwithpreviousstudiesinthis
field.
The last two contributions in this volume provide an overview of the biotech-
nologicalandbiomedicalapplicationsofcryogels.Cryogelswiththeirlargepores
open up a range of applications, e.g., isolation of microbial cells, capturing of
cancer cells, use as matrices for immobilized cell reactors, and environmental
separation. These applications of cryogels are reviewed in chapter “Cryogels for
Biotechnological Applications.” The unique mechanical properties of PVA
cryogelsmakethemanattractivecandidateforbiomedical,andespeciallymedical
device applications. In chapter “Poly(Vinyl Alcohol) Cryogels for Biomedical
Applications,” the formation process and processing parameters of PVA cryogels
and their application in orthopedic and cardiovascular devices are reviewed and
discussed.
Theeditorbelievesthatthepresentvolumecoveringabroadrangeoftopicsin
thefieldofcryogelswillcontributetoabetterunderstandingofthedevelopments
achievedduringthepasttwodecadesinthesynthesisandapplicationsofcryogels.
I also hope that this work will promote research in this rapidly developing area.
Iwouldliketothankalltheauthorswhohavecontributedtothisexcitingvolumeon
polymericcryogels.
Istanbul,Turkey OguzOkay
Contents
ABriefHistoryofPolymericCryogels. . . . . . . . . . . . . . . . . . . . . . . . . . 1
VladimirI.Lozinsky
BasicPrinciplesofCryotropicGelation. . . . . . . . . . . . . . . . . . . . . . . . . 49
VladimirI.LozinskyandOguzOkay
SynthesisandStructure–PropertyRelationshipsofCryogels. . . . . . . . . 103
OguzOkayandVladimirI.Lozinsky
KineticAnalysisofCryotropicGelationofPoly(VinylAlcohol)/Water
SolutionsbySmall-AngleNeutronScattering. .. . . .. . . . .. . . .. . . . .. 159
ClaudioDeRosa,FiniziaAuriemma,andRoccoDiGirolamo
CryogelsviaUVIrradiation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
PetarD.PetrovandChristoB.Tsvetanov
InorganicCryogels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
OlegA.Shlyakhtin
CryogelsforBiotechnologicalApplications. . . . . . . . . . . . . . . . . . . . . . 245
BoMattiasson
Poly(VinylAlcohol)CryogelsforBiomedicalApplications. . . . . . . . . . . 283
WankeiWan,A.DawnBannerman,LifangYang,andHeliumMak
Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
vii
A Brief History of Polymeric Cryogels
VladimirI.Lozinsky
Contents
1 IntroductoryRemarks........................................................................ 2
2 TypesofInitialSystemsCapableofBeingPrecursors
forthePreparationofCryogels.............................................................. 4
2.1 Polymeric/BiopolymericCryogelsFormedby
Freeze–ThawAgingofColloidSols.................................................. 6
2.2 CryogelsPreparedfromMonomericPrecursors...................................... 7
2.3 PreparationofCryogelsbyCovalentCrosslinkingofHighMolecularWeight
Precursors............................................................................... 8
2.4 Physical(Noncovalent)PolymericCryogels.......................................... 22
2.5 Ionic(Ionotropic)Cryogels............................................................ 36
3 ConcludingRemarks......................................................................... 37
References........................................................................................ 38
Abstract Polymeric cryogels, the gels formed in moderately frozen gelling sys-
tems, have been empirically known for many decades, but systematic scientific
researchonvariouscryogelsandthepeculiaritiesofcryotropicgelformationonly
commencedatthebeginningofthe1980s.Thishistoricalreviewbrieflydescribes
the principal stages of the studies on these very interesting gel materials. It also
discusses some mechanisms of their formation, as well as summarizes published
data on the main representatives of chemically crosslinked (covalent), ionically
linked,andnoncovalent(physical)cryogels.
Keywords Polymeric cryogels (cid:129) Cryogel history (cid:129) Moderately frozen gelling
systems(cid:129)Cryotropicgelationprocesses
V.I.Lozinsky(*)
LaboratoryforCryochemistryof(Bio)Polymers,A.N.NesmeyanovInstituteof
OrganoelementCompounds,RussianAcademyofSciences,VavilovStreet28,119991
Moscow,RussianFederation
e-mail:[email protected]
O.Okay(ed.),PolymericCryogels,AdvancesinPolymerScience263, 1
DOI10.1007/978-3-319-05846-7_1,©SpringerInternationalPublishingSwitzerland2014
2 V.I.Lozinsky
1 Introductory Remarks
Polymeric cryogelsare the gel systems formed via the cryogenic treatment(mod-
erate freezing—frozen storage—thawing) of solutions or colloidal dispersions of
the appropriate precursors [1]. On a microscopic level, moderately frozen molec-
ular or colloid solutions are heterophase systems containing both solids (i.e., the
polycrystalsoffrozensolvent)andsomeunfrozenfractioncalled“unfrozenliquid
microphase”[2],wherethesolutesareconcentrated.Thus,gelationcanonlyoccur
withinthelatterunfrozenregionsofthesystemwhilethecrystalsoffrozensolvent
act as porogens. Such specific conditions of gel formation are the key factors in
determining the rather unusual heterophase macroporous morphology of the
resultingpolymermaterials,thewholesetoftheirphysicochemicalcharacteristics
and,asaconsequence,theiroperationalcapabilities.Thepresentvolumedealswith
thediverseaspectsofpreparation,properties,structure,andpracticalimplementa-
tionofvariouscryogelsbasedonsyntheticorganicorinorganicpolymers,aswell
as on natural biopolymers. Taking into account the fact that the number of the
works published in this field has grown almost exponentially during recent years
(Fig. 1a), it is reasonable to first give a brief historical overview of these gel
systems, which are very interesting both from the fundamental and applied view-
points. Moreover, the authors of some recent publications devoted mainly to the
applied aspects often seem to be unaware of the pioneering studies and main
scientific sources. It is hoped that this chapter will also contribute to a better
understanding of the developments achieved in cryotropic gel formation over the
pastthreedecades.
In many cases, it is difficult to indicate which exactly was the very first
communication on some experimentally observed phenomenon, especially if it
was discovered many years ago in the pre-electronic era, and the report appeared
in an issue hardly available now, or if it was patented locally in a language not
commonlyused.Thepresentbriefhistoricalinformationcertainlyhasnoclaimto
be an exhaustive review of all the early pioneering publications on cryogenically
produced gel matrices. Nevertheless, we can assert that the term “cryogel” was
most probably applied for the first time in a paper published in 1984 to designate
polymeric materials prepared via chemical crosslinking of macromolecular pre-
cursorsinmoderatelyfrozenorganicmedia[4].Thetermwascreatedbycombining
“cryo”(fromtheGreekkryos,meaningfrostorice)and“gel,”thushighlightingthe
specific formation conditions for the gels of this family. Besides the mentioned
article, different terms were used for gels formed in frozen systems (mainly,
aqueous ones): cryocoacervates [5], cryocoagulates [6], cryo-concentrated gels
[7, 8], anomalous gels [9], freeze–thaw gels [10], etc. However, since the end of
the1980stheterm“cryogel”hasbecomemoreandmorepopular(Fig.1b).
It should also be noted that several other materials are currently called
“cryogels.”Specificexamplesareasfollows:
