Experimental

Synthesis and puriation

The ore-shell partiles were synthesized in a two-step reationas desribed in ref. [17℄.

The ore partiles were obtained by emulsion polymerization and used as seed for the

radial polymerizationof the ross-linked shell.

Chemial

N

-isopropylarylamide (NIPAM; Aldrih),

N, N ^′

-methylenebisarylamide (BIS; Fluka), sodium dodeyl sulfate (SDS; Fluka), and potassiumperoxodisulfate (KPS; Fluka) were

used as reeived. Styrene (BASF) was washed with KOH solution and distilled prior

to use. Water was puried using reverse osmosis (MilliRO; Millipore) and ion exhange

(MilliQ;Millipore).

Core latex

Emulsionpolymerizationhas been doneusing a1-Laskequipped withastirrer,areux

ondenser,andathermometer. Thereipefortheorelatexisgiveninthefollowing: SDS

and NIPAM were dissolved in pure water with stirring and the solution is degassed by

repeated evauation under nitrogen atmosphere. After addition of styrene, the mixture

is heated to 80

o C

^under ^an ^atmosphere ^of ^nitrogen. ^The ^initiator ^KPS ^dissolved ⁱⁿ

mL

^of ^water ^is ^added ^while ^the ^mixture ^is ^stirred ^with ³⁰⁰

rpm

^. ^After ⁸

h

^the

latex is ooled to room temperature and ltered through glass wool to remove traes of

oagulum. Puriationwasdonebydialysisofthe latexagainst2.5

· 10 ⁻³ M

^KCl^solution

for approximately 3 weeks (Mediell, 12000-14000

Dalton

^). ^The ^masses ^of ^the ^dierent

reatants are summarizedin the table 2.1.

Core-shell latex

Table 2.2:Synthesis of the ore-shell Laties.

Core-shell Latex KS1 KS2 KS3 KS4

(ross-linking[

mol.%

^℄) ^1.25 ^2.5 ⁵ ^2.5

CoreLatex [

wt.%

^℄ ^20.1 ^18.9 ²¹ ^19.5

CoreLatex [

g

^℄ ^199.0 ^211.5 ^190.5 ^205.1

NiPA [

g

^℄ ^38.0 ^38.0 ^38.0 ^19.0

BIS [

g

^℄ ^0.6480 ^1.2959 ^2.5885 ^0.6470

KPS in10

ml

2

^O^[

g

^℄ ^0.3834 ^0.3814 ^0.3812 ^0.3838

2

^O^[

g

^℄ ^542.4 ^535.8 ^568.2 ^363.5

m P S /m shell

^1.06 ^1.03 ^- ^1.05

The seeded emulsion polymerization for the ore-shell system under onsideration here

wasdoneusing100

g

^of^the^ore^latex^diluted^with ³²⁰

g

^of^deionized^water ^together^with

g

^of ^NIPAM ^and ^1.43

g

^of ^BIS. ^No ^additional^SDS ^was^added ⁱⁿ ^this ^step. ^After ^this

stirred mixturehas been heated to 80

o C

^,^the ^reation^is ^started^by ^the ^addition^of ^0.201

g

^of ^KPS ^(dissolved ⁱⁿ ¹⁵

mL

^of ^water) ^and ^the ^entire ^mixture ^is ^allowed ^to^stir ^for ⁴

h

at this temperature. After ooling to room temperature the latex has been puried by

exhaustiveserumreplaementagainstpuriedwater (membrane: ellulosenitratewith a

0.10-

µm

^pore ^width ^supplied ^by ^Shleiher ^and ^Shuell). ^The ^ells ^ontain ⁷⁵⁰

ml

^. ^The

puriationwas performedonira 10

wt.%

^solution^under^1, ²

bar

^nitrogen^and ^used ^to

onentrate the initialsolutions and to adjust the salt onentration. The masses of the

dierentreatantsusedforthesynthesisofthedierentore-shellsystemsaresummarized

in the table 2.2.

Methods

Transmissioneletron mirosopy

Samplesfor TEMwere prepared by plainga drop ofthe 0.2

wt.%

^solution ^on^a

arbon-oatedoppergrid. Afterfewseonds,exess solutionwasremoved by blottingwithlter

paper. Theryo-TEMpreparationwasdoneondilutesamples(0.2

wt.%

^). ^The^sample^was

kept at roomtemperature and vitried rapidly by the methoddesribed previously [66℄.

AfewmirolitersofdilutedemulsionwereplaedonabareopperTEMgrid (Plano,600

mesh) held by the tweezers of the ControlledEnvironmentVitriationSystem (CEVS).

The dimensions of the holes where the sample is absorbed and vitried are

35 × 35 × 10 µm

^. ^The ^exess ^liquid^was ^removed ^with ^lter^paper. ^Typially ^the ^lm^thikness ^where

the partiles are investigated ranges between 1

µm

^and ^the ^diameter ^of ^the ^partiles

(

∼

¹⁰⁰

nm

^). ^This ^sample ^was ^ryo-xed ^by ^rapid ^immersing^into^liquid ^ethane^ooled ^to

-180

o C

ⁱⁿ ^a ^ryo-box ^(Carl ^Zeiss ^NTS ^GmbH). ^The ^speimen ^was ^inserted ^into ^a

ryo-transfer holder (CT3500, Gatan, Munih, Germany) and transferred to a Zeiss EM922

EFTEM (Zeiss NTS GmbH, Oberkohen, Germany). Examinations were arried out at

temperatures around -180

o C

^. ^The ^TEM ^was ^operated ^at ^an ^aeleration ^voltage ^of ²⁰⁰

kV

^. ^Zero-loss^ltered^images^were^taken ^under^redued^dose^onditions⁽

<

²¹⁰⁰⁰

e ⁻ /nm ²

⁾

with an aperture

α ₀ = 10 mrad

^at ^a^magniation ^of

16000X

^. ^All ^images^were ^reorded

Table 2.3:Summary of the dierent parameters used for the normalization of the sattering

in-tensity prole (see textfor further details).

Systems

c [g/cm ³ ] crosslinking [mol.%] _m ^m ^core

shell N/V [nm ⁻³ ]

digitallyby a bottom-mounted 16bit CCDamera system (UltraSan 1000, Gatan). To

avoid any saturation of the gray values all the measurements were taken with intensity

below 15000, onsidering that the maximum value for a 16 bit amera is

2 ¹⁶

^. ^Images

havebeen proessedwithadigitalimagingproessingsystem (DigitalMirograph 3.9for

GMS1.4, Gatan). The experiment at45

o C

^were ^performedⁱⁿ^an ^Oxford^CT-3500 ^(now:

Gatan, Pleasanton, CA) ryo-holder, and were examined in an FEI (The Netherlands)

T12 G

2

dediated ryogeni-temperature transmissioneletron mirosope.

Dynami light sattering

Dynami light sattering (DLS) was done using a Peters ALV 5000 light sattering

go-niometerequipped with a He-Ne laser (

λ =

^632.8

nm

^). ^The temperature was ontrolled with an auray of 0.1

o C

^. ^The ^samples^were ^highly^diluted ⁽

c = 2.5.10 ⁻³ wt.%

⁾^to

pre-vent multiple sattering and ltered through a

1.2 µm

^lter ^to ^remove ^dust. ^The ^salt

onentration in KCl was set to 10

−4 mol.L ⁻¹

^and ^5.10

⁻² mol.L ⁻¹

^. ^The measurements were performedat asattering angleof 90

o

for temperatures between 10 and 50

o C

Small-angle X-Ray sattering

Small-angle X-Ray sattering experiments have been performed on both ore and

ore-shellsystems. MostoftheSAXSmeasurementsreportedherehavebeen performedatthe

ID2beamlineatthe EuropeanSynhrotronRadiationFaility(ESRF,Grenoble, Frane).

The diameterof the X-ray beam was 150

µm

^and ^the ^inident ^wave ^length ^equals ^to ^0.1

nm

^. ^SAXS ^pattern ^were ^reorded ^with ^a two-dimensional amera loated at a distane of 5

m

^from^the ^sample ^within^an ^evauated ^ight^tube. ^The ^bakground ^sattering ^has

been subtrated from the data and orretions were made for spatialdistortions and for

the detetor eieny. The onentrations of the laties varies between 2 and 6

wt.%

(see Table 2.3). For the latex onentrations used here we assume that the inuene of

interpartiular interferenes an be dismissed without problems and that the struture

fator

S(q)

^is ^equal^to ¹^[17, ^67℄.

In order to hek the detetor the same ore solution has been measured on a modied

Kratkyamerafor

q

^between ^0.03 ^and⁴

nm ⁻¹

^. ^The ^desription^of ^the ^amera^and^of ^the

evaluationof the sattering isgiven elsewhere [17℄.

The density of the shell has been alulated onsidering the value of the density of the

polystyrene ore (1.0525

g/cm ³

^),^the ^density ^of^the ^ore-shell ^for^the^KS2 ^at²⁵

^o C

^(1.098

g/cm ³

⁾ ^and ^the ^mass ^ratio

m P S /m shell

^determined gravimetrially (1.03) using the for-mula:

̺ shell = 1 − (m P S /m shell )/(1 + m P S /m shell )

̺ ⁻¹ _core−shell − ̺ ⁻¹ _core (m P S /m shell )/(1 + m P S /m shell )

^(2.1)

Theshell densityderivesfromthis alulationisequalto1.149

g/cm ³

^. ^The ^same

alula-tion performed this time onsidering the density of the ore partiles (1.059

g/cm ³

⁾ ^and

the mass ratio between the orepartiles and the shell polymerizedin the seondstep of

thepolymerization

m core /m shell

^(1.15)^gives^a^value^of^1.147

g/cm ³

^. ^The^same^alulation

performed on the KS1 onsidering the density of the ore-shell measured at 20

o C

^(1.098

g/cm ³

⁾ ^and ^the ^dierent mass-ratios (

m P S /m shell = 1.06

m core /m shell = 1.19

⁾ ^gives

re-spetively adensity of 1.151 and 1.148

g/cm ³

^. ^The ^dierent ^results ^for ^the ^two ^systems

obtained fromthe two alulationsare in good agreement withinthe experimentalerror,

whihis mostly omingfrom the determinationof the mass ratioby gravimetry. Forthe

rest of the work the density for the PNIPAM and for the ross-linked shell will be

on-sidered equalto 1.149

g/cm ³

^. ^In ^this ^way ^the ^density ^value ^of ^the ^shell ^is ^slightly ^higher

than the density of pure PNIPAM in water as determined by Shibayama and al. (1.140

g/cm ³

⁾^[1℄, ^whih ^is ^natural^onsidering ^the ross-linkingof the system.

The eletroni density has been alulated in

electrons/nm ³

^using ^the ^formula:

̺ e = N A .̺.n e ⁻

M

^(2.2)

with

̺

^the ^density ^of ^the ^system,

M

^and

n e ⁻

^the ^moleular ^weight ^and ^the ^number

of eletrons per onstituting moleules. From the density values the exess eletroni

density

∆̺ e

^of ^the ross-linked shell follows as 45.5

e ⁻ /nm ³

^. ^The ^respetive ^quantity ^of

polystyrene is 7.5

e ⁻ /nm ³

^at ²⁵

^o C

^. ^These^numbers ^dene^the ^ontrastⁱⁿ^SAXS ^of^these

polymers in water.

Thesatteringdensityprolehavebeennormalizedbythenumberofpartilespervolume

N/V

⁽ⁱⁿ

nm ⁻³

⁾ ⁱⁿ ^order ^to ^obtain ^the ^sattering ^of ^one ^single ^partile

I ₀

^. ^The ^quantity

N/V

^derives ^from ^the ^mass onentration of the dispersion

c

⁽ⁱⁿ

g/cm ³

^), ^from ^the ^ratio

ore/shell

m core /m shell

^determined^by ^gravimetry^,^and ^from^the ^radius^of ^the^ore

R c

^and

itsdensity (1.059

g/cm ³

⁾^as ^follows:

N/V = c.(m _{P S} /m _shell )/(1 + m _{P S} /m _shell )

(4/3)π̺ c R ³ _c

^(2.3)

Tothispurposethevalueof

R c

^was^onsidered^equal^to⁵²

nm

^from^the^gaussian^t^of^the

size distribution determined from the ryoTEM analysis (see setion 2.2). The dierent

parameters for the normalization of the urves are indiated in the table 2.3. Note that

themassrationore/shelloftheKS3hasnotbeendeterminedgravimetriallybutderived

fromthe phase diagrampresent inthe setionrystallization (see setion 2.3).

Im Dokument Structure, Dynamics and Association of Thermosensitive Core-Shell Particles (Seite 11-15)

N

N, N ′

o C

mL

rpm

h

· 10 −3 M

Dalton

mol.%

wt.%

g

g

g

ml

2

g

2

g

m P S /m shell

g

g

g

g

o C

g

mL

h

µm

ml

wt.%

bar

wt.%

wt.%

35 × 35 × 10 µm

µm

∼

nm

o C

o C

kV

<

e − /nm 2

α 0 = 10 mrad

16000X

c [g/cm 3 ] crosslinking [mol.%] m m core

shell N/V [nm −3 ]

2 16

o C

2

λ =

nm

o C

c = 2.5.10 −3 wt.%

1.2 µm

−4 mol.L −1

−2 mol.L −1

o

o C

µm

nm

m

wt.%

S(q)

q

nm −1

g/cm 3

o C

g/cm 3

m P S /m shell

̺ shell = 1 − (m P S /m shell )/(1 + m P S /m shell )

̺ −1 core−shell − ̺ −1 core (m P S /m shell )/(1 + m P S /m shell )

g/cm 3

g/cm 3

m core /m shell

g/cm 3

o C

g/cm 3

m P S /m shell = 1.06

m core /m shell = 1.19

N, N ^′

· 10 ⁻³ M

e ⁻ /nm ²

α ₀ = 10 mrad

c [g/cm ³ ] crosslinking [mol.%] _m ^m ^core

shell N/V [nm ⁻³ ]

2 ¹⁶

c = 2.5.10 ⁻³ wt.%

−4 mol.L ⁻¹

⁻² mol.L ⁻¹

nm ⁻¹

g/cm ³

^o C

g/cm ³

̺ ⁻¹ _core−shell − ̺ ⁻¹ _core (m P S /m shell )/(1 + m P S /m shell )

g/cm ³

g/cm ³

g/cm ³

g/cm ³

g/cm ³

g/cm ³

g/cm ³

electrons/nm ³

̺ e = N A .̺.n e ⁻

n e ⁻

e ⁻ /nm ³

e ⁻ /nm ³

^o C

nm ⁻³

I ₀

g/cm ³

g/cm ³

N/V = c.(m _{P S} /m _shell )/(1 + m _{P S} /m _shell )

(4/3)π̺ c R ³ _c