Solubility behavior of amphiphilic block and random copolymers ...

Solubility Behavior of Amphiphilic Block and Random 

Copolymers Based on 2-Ethyl-2-oxazoline and 2-Nonyl-2- 

oxazoline in Binary Water–Ethanol Mixtures 

HANNEKE M. L. LAMBERMONT-THIJS, 1,2 RICHARD HOOGENBOOM, 1,2 CHARLES-ANDRÉ FUSTIN, 3 

CÉCILE BOMAL-D’HAESE, 3 JEAN-FRANÇOIS GOHY, 1,3 ULRICH S. SCHUBERT 1,2,4 

1 Laboratory of Macromolecular Chemistry and Nanoscience, Eindhoven University of Technology, 

P.O. Box 513, 5600 MB Eindhoven, The Netherlands 

2 Dutch Polymer Institute (DPI), John F. Kennedylaan 2, 5612 AB Eindhoven, The Netherlands 

3 Unité de Chimie des Matériaux Inorganiques et Organiques (CMAT), Université catholique de Louvain (UCL), 

Place Pasteur 1, 1348 Louvain-la-Neuve, Belgium 

4 Laboratory of Organic and Macromolecular Chemistry, Friedrich-Schiller-University Jena, 

Humboldtstr. 10, 07743 Jena, Germany 

Received 12 September 2008; accepted 23 October 2008 

DOI: 10.1002/pola.23168 

Published online in Wiley InterScience (www.interscience.wiley.com). 

ABSTRACT: The solution properties of random and block copolymers based on 2- 

ethyl-2-oxazoline (EtOx) and 2-nonyl-2-oxazoline (NonOx) were investigated in 

binary solvent mixtures ranging from pure water to pure ethanol. The solubility 

phase diagrams for the random and block copolymers revealed solubility (after heating), 

insolubility, dispersions, micellization as well as lower critical solution temperature 

(LCST) and upper critical solution temperature behavior. The random and block 

copolymers containing over 60 mol % pNonOx were found to be solubilized in ethanol 

upon heating, whereas the dissolution temperature of the block copolymers was 

found to be much higher than for the random copolymers due to the higher extent of 

crystallinity. Furthermore, the block copolymer containing 10 mol % pNonOx exhibited 

a LCST in aqueous solution at 68.7 C, whereas the LCST for the random 

copolymer was found to be only 20.8 C based on the formation of hydrophobic microdomains 

in the block copolymer. The random copolymer displayed a small increase in 

LCST up to a solvent mixture of 9 wt % EtOH, whereas further increase of ethanol 

led to a decrease in LCST, which is probably due to the ‘‘water-breaking’’ effect 

causing an increased attraction between ethanol and the hydrophobic part of the 

copolymer. In addition, the EtOx-NonOx block copolymers revealed the formation of 

micelles and dynamic light scattering demonstrated that the micellar size is increasing 

with increasing the ethanol content due to the enhanced solubility of EtOx. 

VC 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 515–522, 2009 

Keywords: amphiphilic copolymers; LCST; micelles; polyamides; poly(2-oxazoline); 

self-organization; solution properties; UCST; water–ethanol 

Correspondence to: R. Hoogenboom (E-mail: r.hoogenboom@tue.nl) 

or U. S. Schubert (E-mail: u.s.schubert@tue.nl) 

Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 47, 515–522 (2009) 

VC 2008 Wiley Periodicals, Inc. 

515

516 LAMBERMONT-THIJS ET AL. 

INTRODUCTION 

The solution properties of amphiphilic copolymers, 

such as solubility and aggregation, are of 

major importance for their use in, for example, 

personal care, medical, or pharmaceutical applications. 

In addition, such applications require biocompatible 

polymers and nontoxic solvents like 

water–ethanol mixtures. Surprisingly, little is 

known about solution properties of amphiphilic 

copolymers in water–ethanol mixtures despite 

that it is well-known that such mixtures exhibit 

interesting abnormal properties due to the presence 

of hydration shells around the ethanol 

molecules. 1–3 Thepresenceofsuchshellsresultin 

solubility maxima for drug molecules in water– 

ethanol mixtures. 4–6 To gain more detailed knowledge 

and understanding on the effects of binary 

solvent mixtures on solution properties of polymers, 

systematic investigations are required in 

which the composition of both the polymer and 

the solvent mixture should be varied. Poly(2-oxazolines) 

facilitate the research on solution properties 

because of the ease and versatility to vary the 

side groups, and thus, the polymer properties. By 

simply changing the length of the alkyl side 

group, the nature of the polymers can be varied 

from hydrophilic with methyl and ethyl substituents 

to hydrophobic polymers with longer alkyl or 

aromatic side groups. 7,8 In literature, a large 

number of studies discuss structure-property relationships 

for poly(2-oxazolines), in some cases also 

using systematic variations in monomer composition. 

9,10 Such copolymer series mainly focused up 

to now on the combination of hydrophilic and 

hydrophobic monomers because amphiphilic 

copolymers exhibit interesting thermal, surface, 

and solution properties. For example, the lower 

critical solution temperature (LCST) in water, 

which is based on the hydrophilic–hydrophobic 

balance of various copolymers, has been studied 

in detail. 11,12 It is known that the LCST can be 

controlled by incorporating specific compositions 

of hydrophilic and hydrophobic 2-oxazoline monomer 

units within the main chain, 13–16 as in the 

case of other thermosensitive polymers. 17 In addition, 

such amphiphilic poly(2-oxazoline)s have 

gained interest for use in, for example, aqueous 

self-assembly, micellar catalysis, drug delivery, 

and hydrogels. 18–30 

In a previous solubility screening, a series of 

gradient 2-methyl-2-oxazoline or 2-ethyl-2-oxazoline 

in combination with 2-phenyl-2-oxazoline 

copolymers was investigated revealing that the 

solution properties of these amphiphilic gradient 

copolymers could be tuned in a wide range by 

only changing the composition of the water–ethanol 

mixtures. 31 Here,wereportsystematicinvestigations 

on the solution properties of 2-ethyl-2- 

oxazoline (EtOx) and 2-nonyl-2-oxazoline (NonOx) 

containing random and block copolymers. The solution 

properties of these copolymers were investigated 

in water–ethanol mixtures ranging from 

pure water to pure ethanol (steps of 20 wt %). 

This systematic screening for random and block 

copolymers with similar compositions allows a 

detailed investigation of the effect of solvent composition 

as well as the polymer structure, which 

has not been reported before. Different solution 

properties were investigated such as LCST, selfassembly, 

and the formation of dispersions. Furthermore, 

the self-assembled structures were 

analyzed by DLS to correlate the hydrodynamic 

radius of the formed aggregate with the effect of 

the binary water ethanol solvent mixture. 

EXPERIMENTAL 

The synthesis and characterization of the EtOx- 

NonOx random and block copolymers was already 

reported elsewhere. 32 

Instrumentation 

The solubility screening was performed by heating 

the polymer (5.0 0.2 mg) in a solvent mixture 

of ethanol (Biosolve) and deionized water (1.0 

mL). The investigated temperature range was 

20–75 C with heating and cooling steps of 1 C 

min 1 . During these controlled heating and cooling 

cycles (two cycles per sample), the transmission 

through the solutions was monitored in a 

Crystal16 from Avantium Technologies. 31,33 All 

vials were visually inspected after the heating 

program to facilitate the interpretation of the 

observed transmission profiles. A more detailed 

solubility screening was performed for selected 

samples in a broader temperature range from 

20 Cto100 C. The presented upper critical solution 

temperature (UCST) temperatures correspond 

to the dissolution temperatures at 50% 

transmittance from the second heating run. 

Detailed LCST measurements were performed in 

a wider temperature range from 25 Cto105 C 

with heating and cooling steps of 1 Cmin 1 .All 

presented LCST temperatures represent the dissolution 

temperatures at 50% transmittance in 

Journal of Polymer Science: Part A: Polymer Chemistry 

DOI 10.1002/pola

AMPHIPHILIC BLOCK AND RANDOM COPOLYMERS 517 

the second cooling run. The reported dissolution 

temperatures correspond to the temperatures at 

50% transmittance in the first heating run. 

Dynamic light scattering (DLS) measurements 

were performed on a Malvern CGS-3 apparatus 

equipped with a He–Ne laser (632.8 nm) at an 

angle of 90 . A bath of filtered toluene surrounded 

the scattering cell, and the temperature was controlled 

at 25 C. DLS data were analyzed by the 

CONTIN method, as described elsewhere. 34 

RESULTS AND DISCUSSION 

Solubility Screening 

The solution properties of amphiphilic copolymers 

are of major importance for their use in several 

personal care, medical, or pharmaceutical applications. 

Therefore, binary solvent mixtures of 

water and ethanol were chosen because of the low 

toxicity. The solution properties of two complete 

series of random and block copolymers ranging 

from pEtOx to pNonOx in steps of 10 mol % were 

studied. Both series, random and block copolymers, 

consist of similar monomer compositions 

with a degree of polymerization (DP) of 100. In a 

previous work, the polymer properties, such as 

surface, thermal, and mechanical properties, 

were related to the polymer structure. 32 In addition, 

the statistical copolymerization of pEtOx 

and pNonOx was demonstrated to provide truly 

random copolymers. The solubility of the 11 

copolymers from each series (random or block) 

was investigated in solvent mixtures ranging 

from pure water to pure ethanol (steps of 20 wt 

%). The initial solubility screening was performed 

by measuring turbidity of the copolymer samples 

in water–ethanol mixtures as a function of temperature 

in the range from 20 to 75 C. The 

resulting turbidity curves in addition to a visual 

inspection of the obtained solutions revealed the 

solution properties for all different combinations 

of random as well as block copolymers and solvent 

mixtures. The resulting solubility phase diagrams 

are shown in Figure 1 for the pEtOxb-pNonOx 

and pEtOx-r-pNonOx copolymers, 

respectively. At first, the main observations and 

trends in the phase diagram will be discussed, 

whereas more detailed discussions on the different 

phenomena will follow later. The solubility 

phase diagram for the block copolymers (Fig. 1, 

top) reveals that only pEtOx is totally soluble in 

all solvent mixtures. When incorporating 10 mol 

% pNonOx into the block copolymer, a LCST is 


DOI 10.1002/pola 

observed in aqueous solution, that is, macroscopic 

precipitation upon heating. It is known from literature 

that sufficiently long pEtOx (DP [ 100) 

exhibits a LCST temperature in water which can 

be tuned by the polymer length, composition, or 

solvent mixtures. 13,15,16 Furthermore, when a 

hydrophobic monomer is included in the polymer 

chain, the LCST temperature is lowered 13,35,36 

due to the decreased amount of hydrogen bonding 

with water. In the solubility phase diagram, it 

can be seen that the pEtOx does not exhibit a 

LCST but when incorporating 10 mol % pNonOx 

the block copolymer exhibits a LCST transition at 

68.7 C in water. A more detailed screening of the 

LCST will be discussed later. The solubility phase 

diagram further demonstrates that increasing 

the amount of pNonOx leads to a decreased solubility, 

which is evident from the fact that the 

block copolymers containing 20 mol % or more 

hydrophobic pNonOx are not soluble in pure 

water. White solutions which contain a precipitate 

are formed for the block copolymers containing 

20–60 mol % pNonOx indicating that the 

pEtOx block might be partially dissolved or 

aggregated into micelles. Increasing the block 

length of the pNonOx (and therefore decreasing 

the block length of pEtOx) leads to clear solutions 

with totally insoluble polymer particles. In general, 

increasing the amount of ethanol improves 

the solubility of the copolymers because ethanol 

can solvate the nonyl side chains. A narrow regime 

is found where the block copolymers (50–70 

mol % pNonOx in 60 wt % EtOH and the block copolymer 

containing 80 mol % pNonOx in 80 wt % 

EtOH) do form stable dispersions. Furthermore, in 

the intermediate regime from nonsoluble or dispersed 

copolymers to soluble solutions, the 

formation of micellar solutions is observed as 

evidenced by the characteristic bluish color and 

translucent appearance of those solutions. According 

to the solubility of pNonOx, it can be concluded 

that the pEtOx part of the block copolymers is dissolved, 

forming the micellar corona, whereas the 

pNonOx part is not soluble and forms the micellar 

core in the specific solvent mixtures that revealed 

the formation of micelles. Those micelles will be 

discussed in more detail further on. 

An interesting observation was made for the 

solubility of pNonOx in pure ethanol; at room 

temperature the pNonOx homopolymer was not 

soluble, but raising the temperature above a specific 

temperature leads to dissolution of the pNonOx. 

During subsequent cooling and heating 

cycles, the pNonOx remained soluble in EtOH.


DLS measurements confirmed the presence of isolated 

pNonOx chains in solution rather than 

aggregated ones (a single population with a 

hydrodynamic radius of 3 nm was observed which 

hasbeenattributedtosinglechains).Thispeculiar 

solubility behavior of pNonOx in ethanol can 

be rationalized as follows. To dissolve the polymer, 

the solvent needs to penetrate into the pNonOx 

crystals which can be facilitated by both the 

increased Brownian motion of ethanol as well as 

the partial melting of the crystals at higher temperatures. 

Once the first solvation shells are 

formed, the polymer dissolution would be accelerated 

and, after full solvation, the polymer would 

remain in solution. This observed effect is similar 

to the formation of hydration shells in the dissolution 

process of poly(ethylene glycol) as described 

in literature. 37 All block copolymers containing 40 

wt % or more NonOx required elevated temperatures 

to become soluble in pure ethanol and 

stayed in solution during the second heating and 

cooling cycle. 

The solubility phase diagram for the random 

copolymers (Fig. 1, bottom) shows general trends 

similar to the ones observed for the block copolymers, 

that is, decreasing solubility with increasing 

pNonOx content, increasing solubility with 

increasing ethanol fraction, and dissolution of the 

pNonOx copolymers in ethanol with elevated temperatures. 

Nonetheless, some clear differences 

between the random and block copolymers were 

also found. In comparison to the block copolymers, 

the random copolymers with a high pNonOx content 

revealed less interactions with the water rich 

solutions. Most of these samples gave clear solutions 

with solid particles indicating that no part 

of the copolymer was hydrated or dissolved. Moreover, 

the solubility phase diagram shows that the 

random copolymers displayed no translucent solutions 

indicating that the random copolymers do 

not form micellar aggregates. In contrast, two of 

the random copolymers containing 60 and 70 mol 

% NonOx reversibly dissolved in 80 wt % EtOH 

upon heating, indicating an UCST. The dissolution 

temperature found for the copolymer containing 

60 mol % pNonOx is 26 C, whereas the polymer 

containing 70 mol % pNonOx revealed a dissolution 

temperature of 67 C due to the higher 

amount of hydrophobic monomer indicating that 

solvation of the pNonOx chains only takes place 

at elevated temperatures. This difference between 

the block and random copolymers can be understood 

by the close proximity of the NonOx units in 

the block copolymer resulting in an insoluble 

block and, thus, micellization. In the random copolymer, 

the insoluble NonOx units are uniformly 

distributed over the chain resulting in a lower 

total solubility. The random copolymer containing 

10 mol % pNonOx exhibited a LCST in water and 

in the binary solvent mixture containing 20 wt % 

EtOH, whereas the block copolymer only revealed 

a LCST transmission in water (LCST of 69.8 C). 

A more detailed investigation of the LCST transition 

focusing on the nature of the copolymer as 

well as the solvent composition was performed 

and will be discussed in detail below. 

Solubilization Temperatures of Random 

and Block Copolymers in Ethanol 

The random copolymers containing 60 mol % or 

more NonOx and the block copolymers with 40 wt 

% NonOx or more dissolved in pure ethanol during 

the first heating step. During subsequent cooling 

and heating steps the copolymers remained in 

solution. The solubilization temperatures for both 

the random and block copolymers were extracted 

from the transmission measurements (the dissolution 

temperature was taken at 50% transmittance) 

and are plotted in Figure 2. The random 

copolymers reveal a lower crystallinity when 

compared with the block copolymers as determined 

by the thermal measurements. 32 The 

decreased crystallinity in the random copolymers 

can be rationalized by the presence of EtOx units 

that disturb the packing in the pNonOx crystallites. 

Therefore, ethanol can easily penetrate into 

the crystals of the random copolymers and the 

copolymers are dissolved at lower temperatures in 

comparison to the block copolymers. This proposed 

correlation between the crystallinity and dissolution 

temperature is further evidenced by the close 

resemblance of the dissolution temperature 

against the composition plots and the melting temperature 

against the composition plots. 32 

Detailed LCST Investigations of Random 

and Block Copolymers 

A more detailed investigation of the LCST temperature 

was performed for the random and block 

copolymers containing 10 mol % NonOx. A series 

of solvent mixtures ranging from 0 to 24% EtOH 

(in steps of 3%) was prepared and the cloud points 

(indicative for the LCST temperature) were determined 

from the transmission plots at 50% transmittance 

in the second heating run. The obtained 

cloud point temperatures are plotted in Figure 3 

for both the random and block copolymers, 


DOI 10.1002/pola


Figure 1. Solubility overview for the EtOx-b-NonOx (top) and EtOx-r-NonOx 

(bottom) copolymer libraries in water-ethanol mixtures (5 mg/mL). 

respectively. The LCST for the block copolymer in 

aqueous solution is 68.7 C, whereas the LCST for 

the random copolymer is only 20.8 C. This difference 

in LCST could be explained by the formation 

of a single hydrophobic pNonOx microdomain per 

block copolymer which makes only a small hydrophobic 

contribution to the cloud point temperature. 

Moreover, DLS investigations confirmed 

that the pNonOx hydrophobic microdomains do 

not further aggregate into a micellar core for 

these solvent compositions because no micellar 

aggregates could be detected. In contrast, the 

Figure 2. Dissolution temperatures for EtOx- 

NonOx random and block copolymers in 100% EtOH 

solution in the first heating run (5 mg/mL). 

Figure 3. LCST as function of wt % ethanol for 

EtOx 90 -b-NonOx 10 and EtOx 90 -r-NonOx 10 . 


DOI 10.1002/pola


nonyl oxazoline is randomly distributed in the 

random copolymer chain resulting in a decreased 

hydrophilicity of the entire chain. Therefore, the 

effect on the cloud point temperature is much 

larger when compared with the block copolymer. 

38,39 The long nonyl side group which is not 

dissolved in the aqueous rich solutions reduces 

the accessibility of the amide groups that form the 

hydrogen bonding with water, which are responsible 

for the LCST behavior. From Figure 3, it can 

be concluded that the cloud point is increasing 

when adding ethanol to the aqueous solution due 

to a better solvation of hydrophilic EtOx block of 

the copolymer as was observed for EtOx-PhOx 

copolymers. 31 The hydrophobic pNonOx domains 

are not significantly affected by adding small 

amounts of EtOH because pNonOx remains insoluble 

in these solvent mixtures. The block copolymer 

exhibits a cloud point up to 12 wt % EtOH 

and thereafter, the polymer stays in solution up to 

a temperature of 100 C. The random copolymers 

showed a small increase in cloud point up to 9 wt 

% EtOH although this increase is less prominent 

in comparison to the block copolymers. Further 

increasing the amount of ethanol above 9 wt % 

revealed a decrease in cloud point. This unexpected 

effect could be explained by the formation 

of hydration shells of water around ethanol molecules 

which is most prominent at low ethanol concentrations. 

3 Therefore, at low EtOH concentrations, 

the ethanol prefers the water environment 

resulting in decreased polarity causing a small 

increase in cloud point temperature due to a better 

solvation of the copolymer. A further increase 

in the amount of ethanol seems to cause ‘‘water 

structure breaking,’’ resulting in an increased 

attraction between the ethanol and the hydrophobic 

part of the polymer. Therefore, a decrease in 

LCST temperature is observed due to the 

decreased interaction between the polymer and 

aqueous solution. A similar effect is described for 

longer n-alcohols (C 4 –C 6 ) at low concentrations 

causing a decrease in LCST for ethylene oxide– 

propylene oxide copolymers. 40,41 

Micelle Formation of the Block Copolymers 

After each transmission measurement, the vials 

were visually inspected and some of the block 

copolymers showed bluish translucent solutions 

in specific solvent mixtures indicating the presence 

of micelles (squares Fig. 1, top). Those solutions 

were investigated by DLS to study the influence 

of binary solvent mixtures and the ratio of 

Figure 4. CONTIN histogram obtained by analysis 

of the DLS data for the EtOx 70 -b-NonOx 30 sample in 

40/60 EtOH/water solution. The first peak in the 

histogram is attributed to single micelles while the 

second peak corresponds to clusters of micelles. 

hydrophilic–hydrophobic block lengths on the 

micellar size. As discussed previously, the micelles 

consist of a pNonOx core and a pEtOx corona. 

DLS revealed the presence of bimodal distributions 

of aggregates for several of the investigated 

samples. Most probably, the smaller distribution 

corresponds to single micelles and the larger population 

is due to clusters of micelles as it is commonly 

observed for poly(2-oxazoline) micelles. 42,43 

In the following, the Rh of the micelles will be 

estimated as the value determined at the maximum 

of the first peak observed in the CONTIN 

histogram (Fig. 4). As expected, larger micelles 

are formed as the content of hydrophobic block is 

increased while keeping the DP constant. In this 

respect, micelles with a Rh of 22 nm are observed 

for the sample with 30 mol % NonOx in 60 wt % 

EtOH solutions, whereas micelles with a Rh of 35 

nm are formed for the sample with 40 mol % 

NonOx in the same solvent mixture. However, 

more interesting is the observed increase in the 

micellar size with the increasing amount of ethanol. 

For example, the Rh of the micelles formed by 

the sample with 30 mol % NonOx increased from 

18 nm to 22 nm when the EtOH content increased 

from 40 wt % to 60 wt %, respectively. Further 

increasing the amount of ethanol to 80 wt % 

EtOH led to a Rh of 2.4 nm, indicating single 

chains in solution. Jordan and coworkers investigated 

the inner structure of MeOx-NonOx block 

copolymers in aqueous solution using SANS and 

concluded that pNonOx blocks are stretched from 


DOI 10.1002/pola


Figure 5. Schematic representation of the investigated micelles demonstrating the 

effect of changing the amount of ethanol. [Color figure can be viewed in the online 

issue, which is available at www.interscience.wiley.com.] 

the surface of the core to the center, which is most 

likely caused by the large nonyl side groups. 44 The 

presence of stretched pNonOx chains in the core 

implies that changing the amount of ethanol will 

probably have a negligible effect on the inner core 

because pNonOx chains are not soluble in these binary 

solvent mixtures. Therefore, the increase in 

micellar size with increasing amounts of ethanol is 

most likely related to the pEtOx corona. The 

pEtOx chains are better soluble in EtOH than in 

water and, therefore, it is proposed that the pEtOx 

will be better solvated with the increasing 

amounts of ethanol causing a stretching of the 

chains, and thus, the micellar size will grow by 

expansion of the corona as depicted in Figure 5. 

As already stated above, the solutions that 

were translucent were initially identified as micelle 

containing solution. To determine if the dispersions 

as marked in the solubility phase diagram 

are not containing large micelles they were 

also measured by DLS. However, these samples 

appeared to be too milky to be measured by DLS 

or were clearly suspensions (big particles visible). 

In addition, the clear solutions that were close to 

translucent samples in the phase diagram indeed 

did not contain the micelles as evidenced by DLS. 

CONCLUSIONS 


DOI 10.1002/pola 

In this contribution, we compared the solution 

properties of random and block pEtOx-pNonOx 

copolymers in binary solvent mixtures ranging 

from pure water to pure ethanol. In the solubility 

phase diagram, different regions could be identified 

from insoluble copolymers or copolymers that 

formed stable dispersions to regions where the copolymer 

is soluble or solubilizes at elevated temperatures. 

The large difference in the solubilization 

temperatures between the random and block 

copolymers could be explained by the reduced 

crystallinity in the random copolymers. Ethanol 

can, therefore, easily penetrate into the random 

copolymers that are dissolved at lower temperatures 

in comparison to the block copolymers. The 

copolymers containing 10 mol % pNonOx (random 

and block) showed a LCST behavior in aqueous 

solution. The significant difference in LCST 

between the random and block copolymer could 

be explained by the formation of hydrophobic 

microdomains in the block copolymer. The formation 

of these microdomains causes a smaller effect 

on the LCST in comparison to the random distribution 

of the nonyl side chains through the polymer 

chain. The cloud points were further investigated 

by increasing the amount of ethanol in 

small steps up to 24 wt % EtOH. We could observe 

an increase in LCST for the block copolymers up 

to a solvent mixture of 12 wt % EtOH after which 

the polymer stayed in solution up to 100 C. The 

random copolymers displayed a small increase in 

LCST up to a solvent mixture of 9 wt % EtOH, 

further increase of the ethanol content led to a 

decrease in LCST temperature which is probably 

due to the ‘‘water-breaking’’ effect causing an 

increased attraction between ethanol and the 

hydrophobic part of the copolymer resulting in a 

decreased LCST temperature. Furthermore, the 

EtOx-NonOx block copolymers revealed the formation 

of micelles in specific binary solvent mixtures. 

All micellar sizes were investigated by DLS 

showing that with increasing ethanol concentration 

the micellar size is increasing. This phenomenon 

is thought to be related to the enhanced solubility 

of EtOx in EtOH which causes expansion 

and less coiling of the EtOx chains.


This work forms part of the research program of the 

Dutch Polymer Institute (DPI), project no. 500 and 543. 

We thank the DPI, NWO, and the Fonds der Chemischen 

Industrie for the financial support. C.-A. Fustin 

and J.-F. Gohy are grateful to the ‘‘Politique Scientifique 

Fédérale’’ for the financial support in the frame of the 

‘‘Interuniversity Attraction Poles Programme (PAI VI/ 

27): Functional Supramolecular Systems’’ and to the 

STIPOMAT ESF Program. C.-A. Fustin is Research 

Associate of the FRS-FNRS. 

REFERENCES AND NOTES 

1. Frank, H. S.; Evans, M. W. J Chem Phys 1945, 13, 

507–532. 

2. Franks, F. Q. Rev Chem Soc 1966, 20, 1–44. 

3. Noskov, S. Y.; Lamoureux, G.; Roux, B. J Phys 

Chem B 2005, 109, 6705–6713. 

4. Escalera, J. B.; Bustamante, P.; Martin, A. J 

Pharm Pharmacol 1994, 46, 172–176. 

5. Romero, S.; Reillo, A.; Escalera, B.; Bustamante, 

P. Chem Pharm Bull 1996, 44, 1061–1064. 

6. Bustamante, P.; Navarro, J.; Romero, S.; Excalera, 

B. J Pharm Sci 2002, 91, 874–883. 

7. Kobayashi, S.; Igarashi, T.; Moriuchi, Y.; Saegusa, 

T. Macromolecules 1986, 19, 535–541. 

8. Jin, R. H. Adv Mater 2002, 14, 889–892. 

9. Hoogenboom,R.MacromolChemPhys2007,208,18– 

25. 

10. Aoi, K.; Okada, M. Prog Polym Sci 1996, 21, 151– 

208. 

11. Caneba, G. T.; Shi, L. In Lower Critical Solution 

Temperature of Polymer-Small Molecule Systems: 

A Review; Research Signpost: Trivandrum, India, 

2002, Chapter 4, pp 63–104. 

12. Schild, H. G. Prog Polym Sci 1992, 17, 163–249. 

13. Park, J.-S.; Kataoka, K. Macromolecules 2006, 39, 

6622–6630. 

14. Lin, P.; Clash, C.; Pearce, E. M.; Kwei, T. K. J 

Polym Sci Part B: Polym Phys 1988, 26, 603–619. 

15. Christova, D.; Velichkova, R.; Loos, W.; Goethals, 

E. J.; Du Prez, F. Polymer 2003, 44, 2255–2261. 

16. Hoogenboom, R.; Thijs, H. M. L.; Jochems, M. J. 

H. C.; van Lankvelt, B. M.; Fijten, M. W. M.; 

Schubert, U. S. Chem Commun 2008, 44, 5758– 

5760. 

17. Fournier, D.; Hoogenboom, R.; Thijs, H. M. L.; 

Paulus, R. M.; Schubert, U. S. Macromolecules 

2007, 40, 915–920. 

18. Saegusa, T.; Ikeda, H. Macromolecules 1973, 6, 808– 

811. 

19. Saegusa, T.; Ikeda, H.; Fujii, H. Macromolecules 

1972, 5, 359–362. 

20. Huang, H.; Hoogenboom, R.; Leenen, M. A. M.; 

Guillet, P.; Jonas, A. M.; Schubert, U. S.; Gohy, J. 

F. J Am Chem Soc 2006, 128, 3784–3788. 

21. Jin, R. H. J Mater Chem 2004, 14, 320–327. 

22. Percec, V.; Bera, T. K.; Butera, R. J. Biomacromolecules 

2002, 3, 272–279. 

23. Chujo, Y.; Sada, K.; Saegusa, T. Macromolecules 

1993, 26, 6315–6319. 

24. Adams, N.; Schubert, U. S. Adv Drug Deliv Rev 

2007, 59, 1504–1520. 

25. Nuyken, O.; Weberskirch, R.; Bortenschlager, M.; 

Schonfelder, D. Macromol Symp 2004, 215, 215– 

229. 

26. Nuyken, O.; Persigehl, P.; Weberskirch, R. Macromol 

Symp 2002, 177, 163–173. 

27. Bonne, T. B.; Luedtke, K.; Jordan, R.; Stepanek, P.; 

Papadakis, C. M. Colloid Polym Sci 2004, 282, 833– 

843. 

28. Bonne, T. B.; Luedtke, K.; Jordan, R.; Papadakis, 

C. M. Macromol Chem Phys 2007, 208, 1402–1408. 

29. Demirel, A. L.; Meyer, M.; Schlaad, H. Angew 

Chem Int Ed Engl 2007, 46, 8622–8624. 

30. Gress, A.; Voelkel, A.; Schlaad, H. Macromolecules 

2007, 40, 7928–7933. 

31. Hoogenboom, R.; Thijs, H. M. L.; Wouters, D.; Hoeppener, 

S.; Schubert, U. S. Soft Matter 2008, 4, 103– 

107. 

32. Fijten, M. W. M.; Kranenburg, J. M.; Thijs, H. M. 

L.; Paulus, R. M.; van Lankvelt, B. M.; de Hullu, 

J.; Springintveld, M.; Thielen, D. J. G.; Tweedie, 

C. A.; Hoogenboom, R.; Van Vliet, K. J.; Schubert, 

U. S. Macromolecules 2007, 40, 5879–5886. 

33. Birch, M.; Fussel, S. J.; Higginson, P. D.; McDowall, 

N.; Marziano, I. Org Process Res Dev 2005, 

9, 360–364. 

34. Berne, B. J.; Pecora, R. J. Dynamic Light Scattering; 

Wiley: Toronto, 1976. 

35. Park, J.-S.; Kataoka, K. Macromolecules 2007, 40, 

3599–3609. 

36. Huber, S.; Jordan, R. Colloid Polym Sci 2008, 286, 

395–402. 

37. Kjellander, R.; Florin, E. J Chem Soc 1981, 77, 

2053–2077. 

38. Ringsdorf, H.; Simon, J. Macromolecules 1992, 25, 

5353–5361. 

39. Ringsdorf, H.; Venzmer, J. Macromolecules 1991, 

24, 1678–1686. 

40. Beom Lee, S.; Cong, S.-C.; Jin, J.-I.; Sohn, Y. S. 

Polym Bull 2000, 45, 389–396. 

41. Bharatiya, B.; Guo, C.; Ma, J. H.; Hassan, P. A.; 

Bahadur, P. Eur Polym J 2007, 43, 1883–1891. 

42. Hoogenboom, R.; Wiesbrock, F.; Huang, H.; Leenen, 

M.A.M.;Thijs,H.M.L.;vanNispen,S.F.G.M.; 

van der Loop, M.; Fustin, C. A.; Jonas, A. M.; Gohy, 

J.-F.; Schubert, U. S. Macromolecules 2006, 39, 

4719–4725. 

43. Fustin, C.-A.; Lefevre, N.; Hoogenboom, R.; Schubert, 

U. S.; Gohy, J.-F. Macromol Chem Phys 

2007, 208, 2026–2031. 

44. Papadakis, C. M.; Ivanova, R.; Luedtke, K.; Mortensen, 

K.; Pranzas, P. K.; Jordan, R. J Appl Crystallogr 

2007, 40, 361–362. 


DOI 10.1002/pola

Solubility behavior of amphiphilic block and random copolymers ...

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