Literature Seminar

2011/8/16

Masaki Kawai

General polymer to Smart polymer~Introduction of polymer chemistry~ 1.Introduction
 2.Organic Synthetic Application
 3. Reversible polymers for Smart polymer
 4.Summery1

1.

Introduction
Reference: 日本化学会 実験化学講座化学講座 4 基礎編Ⅳ 2003 丸善
日本化学会 実験化学講座 28 高分子 1992 丸善
井上祥平 高分子合成化学 改訂版 2011 裳華房
蒲池幹治 高分子化学入門 改訂版 2006 NTS

1-1. What is polymer
・Definition by IUPAC:
A molecule of high relative molecular mass, the structure of which essentially comprises themultiple repetition of units derived, actually or conceptually, from molecules of low relative
molecular mass.

Notes・Generally measure of molecular weight isabout over 10,000.

1. In many cases, especially for synthetic polymers, a molecule can be regarded ashaving a high relative molecular mass if the addition or removal of one or a fewof the units has a negligible effect on the molecular properties. This statement
fails in the case of certain macromolecules for which the properties may be
critically dependent on fine details of the molecular structure.
2. If a part or the whole of the molecule has a high relative molecular mass andessentially comprises the multiple repetition of units derived, actually orconceptually, from molecules of low relative molecular mass, it may be describedas either macromolecular or polymeric, or by polymer used adjectivally.

・Compared with Organic chemistry(so-called)
Polymer chemistry
・Handling macromolecular
・Product property depend on not only construction.(functional group・ structure …etc)
・Be decided only after the distribution of molecular weight is specified, so dynamic and thethermodynamic in the solid and the solution state characteristic is greatly different fromthe monomeric substance.

21-2. Examples of Polymer

Food：starch….amylose

Housing: wood fiber….cellulose(composed byα1→4 D-glucose)(composed by β1→4 D-glucose)

Artificial
Clothing: SilkRayon(artificial silk)(composed by amino acid)(composed by regenerated cellurose)

Almost all things in thispicture are polymer
polymer

1-3. Fundamental knowledge

Average molecularweight
Polymer is analyzed
in the assembly,
Hard to separate into a
monomolecular group・Mn（number-average molecular weight）= ΣNiMi/ΣNiii

・Mw（weight-average molecular weight）= ΣNiMi2 /ΣNiMiii3e.g.):oligomer(MW=1,000)

Mn=4,000…for calculation
Mw=5,000…for dealing with physical property
Mw/Mn=1.25

・Mw/Mn : poly dispersity index
Polymer have no dispertion : Mn= Mw (Mw/Mn=1)
Polymer have dispertion : Mn<Mw
indicator of reaction type・Radical polymerization :Mw/Mn= about2~3・condensation polymerization: Mw/Mn= about 2・Living polymerization:Mw/Mn= about 1.1○Determination of molecular weight
Measurement

Sort of average

Molecular weight range

instrument

Terminal group determinationMn

103~105

NMR

Cryoscopic methodMn<3,000

Cryoscopic apparatus

Ebullioscopic methodMn<3,000Ebuillioscopict apparatus

OsmometryMn104~106

osmometer

Mass spectrometry

Mn

<105

MALDI-TOF MASSLight scattering methodMw

104~107

MALLS

Sedimentation equilibrium methodMw

104~107

ultracentrifugation

Viscometry

Mv

Wide range

viscometer

Mw, MnWide range

HPLC& UV or

Size exclusion chromatography(Gel permeation chromatography)

Differential refractometer42. Synthetic Polymer chemistry~classified into reaction type~2-1. Chain polymerization(radicalic, anionic…etc)
2-2. Sequential polymerization(condensation,addition )2-3. Living polymerization

Chain polymerization

Degree of polymerization

Living polymerization
Sequential polymerization

Degree of conversion

2-1. Chain polymerization(radicalic, anionic…etc)○Characteristic of reaction
・Reactive species, such radical or ion, are occurred from polymerization initiator.
・Reactive species react with monomer one after another to produce polymer
・This reactive species is labile so disappear short time・High molecular weight polymer appear in beginningrecombination
k2

k3

Molecular weightnot to react between two polymers

Number of polymer
Number of molecule・Polymer growth reaction is only occurred with monomer

k1
k4

Degree of polimerization
Degree of polymerization

dismutation
k5
Chain transfer5

2-2. Sequential polymerization(condensation, addition)○Characteristic of reaction
・Chain growth occur polymer-polymer or monomer-polymer.
・Condensation of monomer is rapidly decrease and monomer change oligomer
・Molecular weight gradually increase with reaction progress
・To get high degree of polymerization needs to excellent yield
Number of polymer

Molecular weightmonomer

・Reaction ExampleDegree of polymerization

1)Dehydrohalogenative polymerization
Ozawa, F, et al J. Am. Chem. Soc 2010, 132, 11420

HT: Head-to-tail
TT: Tail-to-tail
HH: Head-to-head

Rieke, R, D et al
J. Am. Chem. Soc. 1995, 117, 233

The catalytic performance is dependent
on the supporting ligand.
Ozawa, O et al. J. Am. Chem. Soc. 2010, 132, 11420

According to table1
・Electronic-effect contribute to yield.
・Coordinating substituents in phenylgroup act good regio-regularity.
62-3. Living polymerization・chain-growth polymerization that propagates with no irreversible chain-transfer orchain-termination reactions.
・degree of polymerization is proportional
to the ratio of the concentrations of monomer consumed and initiator
・Providing the narrowest MW distribution polymer(MW distribution = Mw/Mn).
・The growing point at polymer terminal is always a polymerization activity. (= living)・If monomer is completely consumed, new added monomer reacts with living polymer

Number of polymer

Molecular weight

Growing point

Deactivated growing point
Degree of polymerization

・Reaction Example
1. Living polymerization with titanium complex
Fujita, T et al Angew. Chem. Int. Ed. 2001. 40. 2918

MAO

Living polymerization

7[Cp2TiCl2] produced polyethylenes
having an Mw/Mn value of 3.31-3.45
under the conditions, indicating that
Cp2TiCl2 under these conditions
25℃

50℃

75℃

At 75℃, chain terminatin ortransfer maybe occurred, but
still possessed somecharacteristics of living
A linear relationship between Mn andpolymerization

polymerization time as well as a narrow range ofMw/Mn values were found for all runs,
indicating a living polymerization

2)Living polymerization condensation
Yokozawa, T and Yokoyama, A Chem. Rev. Soc 2009, 109, 5595

As for condensation polymerization, the monomer has reactive group at both tail. It induce
reaction with monomer to monomer at beginning. Afterward, oligomer or monomer reacts witheither in disorder. (It is to say sequential polymerization). For the above mentioned reason,polycondensation cannot be living polymerization intrinsically. However ,if it can inhibit monomer homo
coupling and react monomer with polymer-growing point selectively, it proceed chain polymerization.

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N-terminal is activated andcarbonyl group is deactivated.
(It is to say, homo coupling doesn’toccur)

Polymerization initiator

Molecular weight
dispersity is very small[1]0 ratio relative to MW

The integral ratio
a:b:c:d=3:1:1:2

Uchiyama, M. Yokozawa, T. et al J. Am. Chem. Soc. 2005, 127, 10172

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3. Reversible polymers for Smart polymer
3-1: Introduction
・The development of the above-mentioned reaction lead investigation into polymer
with various physical properties.
One of them is adaptive/stimuli-responsive polymer(= Smart polymer)
・Smart polymer is composed by supramolecular ( non-covalentbond) or Dynamer(covalent bind) . This time, I intend to introduce example of Dynamer○Compared with General polymer synthesis standpoint
General polymer synthesis

Dynamic polymer synthesis（Irreversible）（reversible）

Stable bondDynamic bond

Avoid exchange reaction

Richness of constitutional

To produce chemically welldiversity

defined unique polymer

Pursuing constitutional
diversity

Emphasizing unicity

Supramolecular

Dynamer

Reversible non covalent bondReversible covalent bond(poly association)
Hard to access its
Generally under continuous

reversibility without

equilibrium.

catalyst or stimulus
Lehn, J. –M. et al, Proc. Natl. Acad. Sci.USA 2004, 101, 8270
Lehn, J. –M. et al, Prog. Polym. Sci. 2005 30, 814
Lehn, J. –M. et al, Chem. Soc. Rev. 2007, 36, 151
Rowan, S. J et al, Nature mater 2010, 10, 1410

3-2. ph responsive smart polymer○Polymer Gels with Reversible Sol-Gel Transition and Self-Healing Properties
Chen, Y. et al Macromolecules, 2010, 43, 1191
<Picture of sol-gel transition and Self-Healing properties.><Polymer synthesis>

Acidic catalyst (it give around ph 6) is necessary for the gelation because acylhydrazone formation is very slow atneutral conditions while a catalytic amount of acid drastically accelerated the reaction

・Gel forming
Predetermined amount of bis-acylhydrazine functionalized PEO polymer (A2) and equivalenttris[(4-formylphenoxy) methyl]ethane (B3) were mixed in a certain amount of DMF to form ahomogeneous solution in a container. After catalyst of acetic acid was added and mixed
homogenously, the solution was sealed in the container and placed at ambient temperature
without stirring until a gel was formed.

Viscosity (h) change vs. time during gelating process ofmixture A2 and B3 in DMF (gelator concentration 12 wt %)at 25C. blue circle: no acetic acid was added; red circle:
glacial acetic(apparent ph = ~5 )acid 15% v/v was added.

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・Sol-gel phase transition ability in response to acidity change
The gel used was prepared in 0.5 mL DMF with gelator concentration 12 wt % and acetic acidconcentration 15% v/v (apparent pH ~5). After the gel aged overnight, 5μL of hydrochloric acid(~37%) was added on the gel surface.
The gel completely decomposed into asol in 1.5 h with a final apparentpH 3-4. When 8 μL triethylamine(equivalent to hydrochloric acid) wasadded, the sol transformed into theAppearance of the original gel (left) and the gel after

gel in 20 second.

eight transition cycles (right).

During the repeated transition cycles, white salts of HCl
and triethylamine gradually appeared due to its low
solubility in DME

・Self-Healing
Polymer gel plates
rhodamine B was addedcarbon black was added,
simply putting
them together.

<Detail of experiment>
Each of the gel plates was cut by a blade
into two halves.
Half of the black plate and half of the redplate were spliced in the original roundbottle by simply putting them together andkeeping contactfor 7 h without any outside intervention.

123-3. Thermo responsive smart polymer○Thermally Induced, Reversible Chain Elongation of Amphiphilic Poly (acylhydrazones)
Lehn, J. -M. et al J. Am.Chem. Soc. 2011. 133. 10966

・Acid-catalyzed<Image figure><Reaction>a R = (CH2CH2O)6Me.
Mw: ~3800kDa

Mw: 46050kDa

DP: ~4274

DP: 520

Mw: 31030kDa
DP: 350

Too large for accurate analysis
Fig3 shows effect on Mw, the more Temperature
Fig.2 shows Mw changing in reaction cycle, A.Cis higher the more Mw is higherthat are under r,t, are lower Mw and B is higher Mw

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~Why this component can be polymerize under heating condition (Generally polymer isdecomposed under heating condition. e.g. cyclopentadiene)~
1) Utilization of LCST
・Polyethylene oxide(PEO) have LCST.
(LCST(Lower critical solution temperature) = Critical temperature below which a mixture is miscible.)

ph=11.4

ph=2.0Turbidity diagrams at 660 nm for aqueous solutions of poly(1_2)([1]0 = [2]0= 1.0 mM) under acidic and basic conditions as afunction of heat/cool cycles (rate = 1 ℃/ s).

LCST can make partial higher concentration suddenly by aggregation.

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Molecular dynamic simulation

GH-TΔS

EssESwΔXEX363 －ΔXEX298
wp: weight fraction of ether in the solution

Figure2. Temperature dependence of excess
thermodynamic properties of DME/water solutions
Bedrov, D et al J. Phys. Chem. B, 2003, 107, 3095

LCST in PEO/water solutions is entharpy-driven

2) Stabilization with helical conformation
・This polymer grows with the formation of large bundles of intertwined rods as observed by TEM
・The folded aromatic backbone is thought to shield the acylhydrazone linkages from bulk solution

Angew. Chem. Int. Ed. 2009, 48, 7664

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Helical folded tube
Lehn, J. –M. et al Polym. Int. 2010, 59, 1477

・~Summary~Di(aldehyde) 1 and Di(acylhydrazine) 2
make thermodynamic polymer in acidic condition.

Growing condition)・High temperature.
・Driving force=aggregation (LCST)andmaking helical folded tube.

Decomposition condition)
・Low temperature
・Driving force=deaggregation and easier tointeract with bulk solution.

This polymer is expected to apply hyperthermic drug delivery chemo-mechanical device…etc16

3-3.Photo responsive smart polymer
A dynamic covalent polymer film driven by disulfide metathesis under photo irradiation.
Otuka, H et al, Chem. commun, 2010, 46, 1150

Disulfide-containing polyester (DSPES)

Polymer film image(…not made of this polymer)
Method: Drop casting technique:
The solution pour to glass board kept
level and wait until solvent disappear

Expeliment 1: Confident the exchange reaction of disulfide bond between the main chain
The film of fractionated DSPES [Mn=12 000,Mw/Mn=1.21]
was photoirradiated in hexane at 30 ℃ under
an argon atmosphere. Although the NMR spectrum did notchange, the GPC profiles drastically changed after
photoirradiation for 60 min

SEC profiles of DSPES exposed to UV light for 0 min (blueline), 10 min (green line), 30 min (orange line), and 60 min(red line).
and 60 min (red line).

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Experiment 2 : To demonstrate the re-organizability
The polymer films, consisting of equal quantities of h-DSPES(Mn =60 400, Mw/Mn = 1.06) andl-DSPES (Mn = 8700, Mw/Mn =1.54 ) that showed two apparent peaks in the GPC profile, werephotoirradiated under the same conditions.
After 60 min, the peaks derived from h-DSPES
and l-DSPES clearly fused into aunimodal peak,Two peaks are integrated onepeak (Mn= 16,000)

4.Summery
・The polymer material is widely used for all food, clothing, and housing regardless of nature andartificial.
・The development of a new polymer synthesis method and the development of functional polymerare very important.
・Polymer synthesis can be classified into three reaction type.
・The narrowest molecular weight dispersity is Living polymerization(= the most controlled polymerization) but cannot be controlled satisfactorily still.

・Smart polymer = dynamic character can be accessed when specific external factors
are exist.
・Adaptable reaction is still few
・Difficult to take balance of reaction condition with reaction time・It is possible to provide for the application to drug delivery and stimulus-mendable polymericmaterial, etc. in the future.
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