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J Polym Res (2012) 19:9910 DOI 10.1007/s10965-012-9910-9 ORIGINAL PAPER MesoDyn simulation study on the phase morphologies of miktoarm PEO-b-PMMA copolymer induced by surfaces Dan Mu · Jian-Quan Li · Song Wang Received: 16 November 2011 / Accepted: 11 June 2012 / Published online: 30 June 2012 © Springer Science+Business Media B.V. 2012 Abstract The compatibility of six groups 12 mik- toarm poly(ethylene oxide)-block-poly(methyl methacry- late) (PEO-b-PMMA) copolymers is studied at 400 K via mesoscopic modeling. The values of the order parameters depend on the architectures of the block copolymers deeply, compared with their chain length. Furthermore, the values of order parameters of the copolymer in the same group are the same. A study of plain copolymers induced by 18 neutral surfaces shows that the microscopic phase is influenced by not only the peculiarities of the inducing surface, but also the architecture of copolymers. The degree of surface roughness plays the most significant role on changing phase separation, the rougher the surface, the higher ordered the microscopic phase. However, the 23141 and 23241-type copolymers which are both PEO-rich composition, presents microscopic phase separation as peculiar lamallae phase morphologies induced by every surfaces, included their plain copolymers. Keywords Miktoarm PEO-b-PMMA copolymer · Lamallae phase morphologies · Inducing surface D. Mu (B ) College of Chemistry Chemical Engineering and Material Science, Zaozhuang University, Shandong 277160, China e-mail: [email protected] J.-Q. Li Opto-Electronic Engineering College, Zaozhuang University, Shandong 277160, China S. Wang Institute of Theoretical Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130023, China Introduction Because of the inherent beauty and potential technological applications, applied the molecular self-assembly of block copolymers to form the nanostructured materials is an ac- tive area of research. Thin films of self-organizing diblock copolymers may be suitable for semiconductor applica- tions since they enable patterning of ordered domains with dimensions below photolithographic resolution over wafer- scale areas [1]. Block copolymers are known to gener- ate nanoscale microdomains by microphase separation, if they are annealed at a temperature lower than their order- disorder transition temperatures [2]. Recently, thin films formed by block copolymer with well defined nanostruc- tures have received considerable attention for their potential nano-fabrication applications [311]. In these applications, controlling the morphology of the block copolymer thin film via adjusting the influencing factors to obtain ordered phase-separated microdomain, has significant and potential meaning. PEO and PMMA are both important polymers for syn- thesis and applications in a variety of engineering and biomedical areas [1214]. The study of PEO/PMMA blends is of interest because of the semicrystalline nature of PEO, the weak interactions between these two polymers, and their large difference in the glass transition temperature (T g ), which make such blends a complex system. Our former paper clarified the conflicting conclusions drawn from different laboratories and from different techniques successfully from theoretical view, we found that the blends tend to undergo phase separation at higher temperature, such as 400 K, on the contrary, the PEO/PMMA blends are miscible at lower temperatures [15]. The amphiphilic graft and block copolymers made of PMMA and PEO blocks have received increasing atten-
Transcript
Page 1: MesoDyn simulation study on the phase morphologies of miktoarm PEO-b-PMMA copolymer induced by surfaces

J Polym Res (2012) 19:9910

DOI 10.1007/s10965-012-9910-9

ORIGINAL PAPER

MesoDyn simulation study on the phase morphologies

of miktoarm PEO-b-PMMA copolymer induced

by surfaces

Dan Mu · Jian-Quan Li · Song Wang

Received: 16 November 2011 / Accepted: 11 June 2012 / Published online: 30 June 2012

© Springer Science+Business Media B.V. 2012

Abstract The compatibility of six groups 12 mik-

toarm poly(ethylene oxide)-block-poly(methyl methacry-

late) (PEO-b-PMMA) copolymers is studied at 400 K via

mesoscopic modeling. The values of the order parameters

depend on the architectures of the block copolymers deeply,

compared with their chain length. Furthermore, the values

of order parameters of the copolymer in the same group are

the same. A study of plain copolymers induced by 18 neutral

surfaces shows that the microscopic phase is influenced by

not only the peculiarities of the inducing surface, but also the

architecture of copolymers. The degree of surface roughness

plays the most significant role on changing phase separation,

the rougher the surface, the higher ordered the microscopic

phase. However, the 23141 and 23241-type copolymers

which are both PEO-rich composition, presents microscopic

phase separation as peculiar lamallae phase morphologies

induced by every surfaces, included their plain copolymers.

Keywords Miktoarm PEO-b-PMMA copolymer ·Lamallae phase morphologies · Inducing surface

D. Mu (B)

College of Chemistry Chemical Engineering and Material

Science, Zaozhuang University, Shandong 277160, China

e-mail: [email protected]

J.-Q. Li

Opto-Electronic Engineering College, Zaozhuang University,

Shandong 277160, China

S. Wang

Institute of Theoretical Chemistry, State Key Laboratory of

Theoretical and Computational Chemistry, Jilin University,

Changchun 130023, China

Introduction

Because of the inherent beauty and potential technological

applications, applied the molecular self-assembly of block

copolymers to form the nanostructured materials is an ac-

tive area of research. Thin films of self-organizing diblock

copolymers may be suitable for semiconductor applica-

tions since they enable patterning of ordered domains with

dimensions below photolithographic resolution over wafer-

scale areas [1]. Block copolymers are known to gener-

ate nanoscale microdomains by microphase separation, if

they are annealed at a temperature lower than their order-

disorder transition temperatures [2]. Recently, thin films

formed by block copolymer with well defined nanostruc-

tures have received considerable attention for their potential

nano-fabrication applications [3–11]. In these applications,

controlling the morphology of the block copolymer thin

film via adjusting the influencing factors to obtain ordered

phase-separated microdomain, has significant and potential

meaning.

PEO and PMMA are both important polymers for syn-

thesis and applications in a variety of engineering and

biomedical areas [12–14]. The study of PEO/PMMA blends

is of interest because of the semicrystalline nature of PEO,

the weak interactions between these two polymers, and

their large difference in the glass transition temperature

(Tg), which make such blends a complex system. Our

former paper clarified the conflicting conclusions drawn

from different laboratories and from different techniques

successfully from theoretical view, we found that the blends

tend to undergo phase separation at higher temperature,

such as 400 K, on the contrary, the PEO/PMMA blends are

miscible at lower temperatures [15].

The amphiphilic graft and block copolymers made of

PMMA and PEO blocks have received increasing atten-

Page 2: MesoDyn simulation study on the phase morphologies of miktoarm PEO-b-PMMA copolymer induced by surfaces

Page 2 of 8 J Polym Res (2012) 19:9910

tions for the potential applications in modification of ker-

atoprosthesis [16], drug carriers [17] and biomedical ma-

terials [18, 19]. The study of PEO-b-PMMA copolymer

is of interest because of its crystallization behavior, and

Sun et al. had reported that the crystallization rate and

the degree of crystallinity decreased by an increase of

PMMA content [20], which means the PEO block in PEO-

b-PMMA copolymer is prone to crystallize. Furthermore,

there haven’t been any reports about the inducing effects of

surfaces on the miktoarm PEO-b-PMMA copolymers. We

gained some inspiring results in this paper, which can be

applied into nano-fabrication to improve its function.

Simulation method and model construction

Mesoscale structures are of utmost importance during the

production processes of many materials, such as polymer

blends, block copolymer systems, surfactant aggregates in

detergent materials, latex particles and drug delivery sys-

tems. Mesoscopic dynamics models are receiving increasing

attention, as they form a bridge between microscale and

macroscale properties [21–24]. As a useful simulation tech-

nique for fluids, MesoDyn has been successfully applied to

study the microphase separation of block copolymers in our

former researches [15, 25–28].

Our simulation processes were all carried out with the

MesoDyn package in the Materials Studio commercial soft-

ware provided by Accelrys on an SGI workstation. Meso-

Dyn is a state-of-the-art mesoscale simulation program. It

utilizes a dynamic variant of mean-field density functional

theory with Langevin-type equations to investigate polymer

diffusion, providing a coarse-grained method for the study

of complex fluids, their kinetics, and their equilibrium struc-

tures at large length and time scales. The thermodynamic

forces are found via mean-field DFT, using the Gaussian

chain as a model. The coarse-grained Gaussian chain con-

sists of beads with equal lengths and equal volumes. With

Table 1 Details of PEO/PMMA blending models and their input

parameters of MesoDyn at 400 K

Symbol wt% Input

Number molar ratio of PMMA parameter

1 1/6 93.16 0.00266

2 1/4 90.09 0.00217

3 1/3 87.20 0.00243

4 1/2 81.96 0.00197

5 1/1 69.43 0.00184

6 2/1 53.18 0.00636

7 3/1 43.09 0.00217

8 4/1 36.22 0.00878

9 6/1 27.46 0.01094

10 8/1 22.11 0.00217

a1 b1

b2a2

b3a3

Fig. 1 The schematic miktoarm PEO-b-PMMA copolymer models

used in this study. The black particles represent the PEO component

denoted as A, while the white particles the PMMA component denoted

as B

time evolution, the free energy of the system results in

no discernible changes, the phase separation is considered

completed.

We have obtained the representative chain lengths of

PEO and PMMA chain and the relevant parameters in our

former work [15, 27], and they are list in Table 1. Therefore,

the block copolymer chains are constructed by PEO (de-

noted as “A”) and PMMA (denoted as “B”) components as

A(A4B6)4, A5(B6)2, A3[A(B6)2]2, B(B5A5)4, B6(A5)2 and

B4[B(A5)2]2, named as 11111, 12112, 13114, 21111, 22121

Table 2 The molecular information of miktoarm PEO-b-PMMA

copolymer

Group Molar ratio Scheme

number of A5 to B6 Architecture Symbol in Fig. 1

Group 1 1:1 A(A4B6)4 11111 a1

1:1 A(A9B12)4 11211

Group 2 1:2 A5(B6)2 12112 a2

1:2 A10(B12)2 12212

Group 3 1:4 A3[A(B6)2]2 13114 a3

1:4 A8[A(B12)2]2 13214

Group 4 1:1 B(B5A5)4 21111 b1

1:1 B(B11A10)4 21211

Group 5 2:1 B6(A5)2 22121 b2

2:1 B12(A10)2 22221

Group 6 4:1 B4[B(A5)2]2 23141 b3

4:1 B10[B(A10)2]2 23241

Page 3: MesoDyn simulation study on the phase morphologies of miktoarm PEO-b-PMMA copolymer induced by surfaces

J Polym Res (2012) 19:9910 Page 3 of 8

Table 3 Information of “ci”, “co”, “gra” and “rg” series surfaces

Type Included Example Scheme Mask type Name explanation

surfaces

ci-xxx ci-444, ci-444 S1 Semicircular balls Four semicircular balls in four

ci-882 surface sides, the radius is 4 nm

co-4xx co-444, co-444 S2 Equal spaced cubic Divided by equal space into four

co-448, columns parts to form two columns in four

co-4412, surface sides, the height is 4 nm

co-4432

co-8xx co-884, co-884 S3 Equal spaced cubic Divided by equal space into eight

co-888, columns parts to form four columns in four

co-8812, surface sides, the height is 4 nm

co-8832

gra-xxx gra-444, gra-444 S4 The same widths, Divided by equal space into four

gra-888 gradually increasing parts in face-to-face sides to four

height columns, small surfaces with gradually

monodirectional increasing height, the highest

asymmetric height is 4 nm

gra-2(xxx) gra-2(444), gra-2(444) S5 The same as gra-xxx type, With the same two symmetric parts

gra-2(448), but monodirectional as gra-444 surface

gra-2(888) symmetric

rg-xxx rg-442, rg-442 S6 Similar as gra-xxx type, The highest height of both face-to-face

rg-884, but bidirectional symmetric sides is 4 nm, the divided surface

rg-16168 in one semi-section is two part

and 23141. Corresponding to these six schematic models in

Fig. 1, they are a1, a2, a3, b1, b2 and b3, respectively. The

latter three models are the component exchange between

“A” and “B” from the corresponding former three. When

double large these six models, we can gain other six mod-

els, A(A9B12)4, A10(B12)2, A8[A(B12)2]2, B(B11A10)4,

B12(A10)2 and B10[B(A10)2]2, named as 11211, 12212,

13214, 21211, 22221 and 23241, respectively. Table 2 lists

the grouping, molar ratio of blocks, molecular architecture,

symbol and corresponding scheme in details.

We designed four series patterned surfaces as substrates,

designated as “ci”, “co”, “gra” and “rg” series, to study

its inducing effects on the compatibility of PEO-b-PMMA

copolymers. The “ci” series of planes used half-spheres with

different radii as a mask that simulated different degrees

of surface roughness. The “co” series had equally spaced

cubic columns as a mask. The columns had different sizes

and heights to simulate different degrees of surface rough-

ness. The “gra” series were planes with different widths to

simulate different degrees of surface roughness. The mask

was generated by gradually increasing the column height

across the plane, so that it resembled stairs viewed side

on. In addition, monodirectional asymmetric planes, such

as gra-444 and gra-888, and monodirectional symmetric

planes, such as gra-2(444), gra-2(448) and gra-2(888), were

considered. The “rg” series were bidirectional symmetric

planes originating from monodirectional symmetric planes,

as used in the “gra” series. The details about these six

Fig. 2 The scheme of six

representative inducing surfaces

Page 4: MesoDyn simulation study on the phase morphologies of miktoarm PEO-b-PMMA copolymer induced by surfaces

Page 4 of 8 J Polym Res (2012) 19:9910

types of designed surfaces were listed in Table 3, and six

representative surfaces (ci-444, co-444, co-884, gra-444,

gra-2(444) and rg-442) were showed in Fig. 2 as schemes

(S1, S2, S3, S4, S5 and S6, respectively).

Simulation results and discussion

We start the simulations by placing the block copolymers

randomly in the simulation box, followed by an equilibra-

tion of 10 ms until the free energy density (RT/Volume)

reaches a relative stable value. The time step is set as 50 ns

to stabilize the numerical calculations. The noise parameter

value is 75.002 by default, is used for the numerical speed

and stability. The adopted grid dimensions are 32 × 32 × 32

nm3, and the size of the mesh over which density variations

are to be plotted in MesoDyn length 1 nm.

The Flory-Huggins interaction parameter, χ data of ten

different compositions which can cover most composition at

400 K [15], and these data can be applied as the input para-

meters to deal with the miktoarm PEO-b-PMMA copolymer

in this work. The connection between the microscale and the

mesoscale is as follows:

IPM = χab RT,

where the parameter χab is calculated by atomistic simula-

tion for each blend composition at different temperature. Ris the molar gas constant, 8.314 J·mol

−1 · K−1

, and T is the

simulation temperature. IPM is the abbreviation of “Input

Parameter of MesoDyn” used to describe the interaction

between beads [15].

The order parameter, P, is defined as the average volume

of the difference between local density squared and the

overall density squared, as given by the equation

Pi = 1

V

∫V

[η2

i (r) − η2

i

]dr,

where ηi is the dimensionless density (volume fraction) of

species i. The larger the value of P, the greater the phase

separation. A decrease in P indicates better compatibility or

miscibility, and the polymer phases mix more randomly.

We define a new parameter to describe the inducing effect

of being induced by surfaces. The order parameter value of

every miktoarm PEO-b-PMMA copolymer not introduced

by inducing surface effects (“plain”) is named as “a”, in

addition, the order parameter value of the corresponding

copolymer with inducing effect is named as “b”. The value

of (b−a)/a is defined as variation rates of order parameter

(VROP for abbreviation). By comparing the VROP values,

we can figure out the effective kind of inducing surfaces

on changing the phase morphology of miktoarm PEO-b-

PMMA copolymer. The larger the value of VROP, the

greater the inducing influence.

Modeling plain miktoarm PEO-b-PMMA copolymer

Figure 3 shows the P values of the 12 plain miktoarm PEO-

b-PMMA copolymers at 400 K. There are several features

in this figure that are worth noting:

(1) The P values of PEO-b-PMMA copolymers in the

same group at 400 K are the same, that is, P11111 =P11211 in Group 1, P12112 = P12212 in Group 2,

P13114 = P13214 in Group 3, P21111 = P21211 in Group

4, P22121 = P22221 in Group 5 and P23141 = P23241

in Group 6. Combined with the iso-density pictures

on the top, it suggests that when the copolymer with

the same architecture, long or short-chain copolymer

could presents the same mesoscale phase morphology.

(2) The order of P is P23141 = P23241 > P22121 = P22221 >

P21111 = P21211 = P11111 = P11211 > P12112 = P12212 >

P13114 = P13214, which can be converted into PGroup6 >

PGroup5 > PGroup4 = PGroup1 > PGroup2 > PGroup3. The

block ratio (PEO to PMMA) of them is 4:1, 2:1,

1:1, 1:1, 1:2 and 1:4, respectively, the more PEO

component in the copolymer, the higher the P value.

The composition of 11111 and 21111-type copolymer

is the same, both having four A5 and four B6

segments, though they have opposite block structure.

However, the compositions of 13114 and 23141-type

copolymer are different, 13114-type copolymer has

one A5 and four B6 segments, 23141-type copolymer

has four A5 and one B6 segments. Therefore, the

situation of P values of these two opposite block

copolymers are different.

(3) The remarkable high P values of Group 6 at 400

K, which is higher than 0.01, and the ordered iso-

density surfaces displayed both reveal its microscopic

phase separation. It can be explained from the special

architecture of 23141 and 23241-type copolymers in

Fig. 3 P values of 12 miktoarm PEO-b-PMMA copolymers at 400

K. Red represents PEO component; green PMMA. The iso-density

surfaces of these copolymers at 400 K are displayed at the top

Page 5: MesoDyn simulation study on the phase morphologies of miktoarm PEO-b-PMMA copolymer induced by surfaces

J Polym Res (2012) 19:9910 Page 5 of 8

Group 6. They both are 4:1 (PEO to PMMA) block

ratio which have the highest PEO component content

in the 12 copolymers, when the temperature becomes

higher, the easier for the chain to move, combined

the nature of PEO block tending to crystallize [20],

then the PEO-rich region could be largened, further

microscopic separation could occur.

Modeling miktoarm PEO-b-PMMA copolymer induced

by surfaces

Subfigures a1, a2, a3, a4 and a5 in Fig. 4 shows the P values

for the 12 miktoarm PEO-b-PMMA copolymers induced by

10 kinds of surface at 400 K, respectively. Subfigures b1,

b2, b3, b4 and b5 show the corresponding VROP values for

these induced copolymers. A reference line is drawn through

R = 1 in subfigures b1, b2, b3, b4 and b5. When an VROPvalue lies above this line, the doping can be considered

to have a reinforcing effect; otherwise, the doping can be

considered to have a weakening effect. Thus, the main ob-

jective of modeling these cases is to determine the effective

surfaces that exerts the most influence on microscopic phase

separation. In addition, we also can explore which type of

miktoarm copolymer suffers the most with such inducing

effect on changing the phase morphology. The following

features of the plots are noteworthy:

(1) The P values of the copolymers in the same group with

the same surface’s inducing effect are also the same

in subfigure a1, a2, a3, a4 and a5. It reveals that the

architecture is more important than the chain length at

400 K. Furthermore, for the copolymers with the same

1:1 (PEO to PMMA) block ratio, that is, 11111, 11211,

21111 and 21211-type copolymers, their P values are

the same.

(2) The general change tendency of P induced by the

same surface effect is P23141 = P23241 > P22121 =P22221 > P11111 = P11211 = P21111 = P21211 >

P12112 = P12212 > P13114 = P13214 at 400 K. How-

ever, the change tendency of the copolymers

induced by co-4412, co-4432, co-8812 and

co-8832 surfaces is different from it, that is,

P23141 = P23241 > P13114 = P13214 > P12112 = P12212 >

P11111 = P11211 = P21111 = P21211 > P22121 = P22221

at 400 K; in addition, the change tendency

of the copolymers induced by rg-442, rg-884

and rg-16168 surfaces is also different, that is,

P23141 = P23241 > P22121 = P22221 > P11111 = P11211 =P21111 = P21211 > P13114 = P13214 > P12112 = P12212

at 400 K. The reason leading to such differences

in the relationship above lies in the particularity of

the inducing surfaces. The 23141 and 23241-type

copolymers both are 4:1 (PEO to PMMA) block ratio

which have the highest PEO component content in the

12 copolymers, whose property depends on property

of PEO. For the copolymers with 1:1 (PEO to PMMA)

block ratio, they have equal opportunity to meet the

same block during mixing process compared with

other type copolymers.

(3) The top two largest P values for the copolymers in-

duced by surfaces are Pco−8832 and Pco−4432, except

23141 and 23241-type copolymer, whose top two

are Pco−8812 and Pci−882. It is the result from the

difference in PEO content. However, Pgra−2(888) and

Prg−16168 present the largest value in “gra” and “rg”

series inducing surface.

(4) The VROP values of the copolymers in the same group

with the same surface’s inducing effect are also the

same in subfigure b1, b2, b3, b4 and b5.

(5) The order of VROP is totally different from the

order of P for the copolymers induced by the

same kind of surface. For co-448, co-4412, co-888,

co-8812, gra-888, gra-2(444), gra-2(888), rg-442

and rg-884 surfaces, the order is VROP13114 =VROP13214 > VROP1 2112 = VROP12212 >

VROP1 1111 = VROP11211 = VROP21111 =VROP21211 > VROP23141 = VROP2 3241 >

VROP22121 = VROP22221; for co-4432, co-

8832, gra-444 and rg-16168 surfaces, the order is

VROP13114 = VROP132 14 > VROP12112 =VROP1 2212 > VROP11111 = VROP11211 =VROP21111 = VROP21211 > VROP2 2121 =VROP2 2221 > VROP23141 = VROP23241; for

co-444, co-884 and gra-2(448) surfaces, the order

is VROP13114 = VROP13214 > VROP12112 =VROP1 2212 > VROP23141 = VROP23241 >

VROP11111 = VROP11211 = VROP211 11 =VROP212 11 > VROP221 21 = VROP2 2221;

for ci-444 surface, the order is VROP12112 =VROP12212 > VROP13114 = VROP1 3214 >

VROP23141 = VROP2 3241 > VROP11111 =VROP11211 = VROP21111 = VROP21 211 >

VROP22121 = VROP22221; for ci-882 surface, the

order is VROP23141 = VROP23241 > VROP12112 =VROP12212 > VROP111 11 = VROP11211 =VROP21111 = VROP212 11 > VROP22121 =VROP22 221 > VROP13114 = VROP13214.

Furthermore, the VROP values are higher than 1,

which means the inducing surface play a reinforcing

effect on the cases as follows: 13114, 13214, 12112

and 12212-type copolymers induced by co-4432

surface; 13114, 13214, 12112 and 12212-type

copolymers induced by co-8812 surface; 13114,

13214, 12112, 12212, 11111, 11211, 21111, 21211,

22121, 22221, 23141 and 23241-type copolymers

induced by co-8832 surface. In addition, there is only

Page 6: MesoDyn simulation study on the phase morphologies of miktoarm PEO-b-PMMA copolymer induced by surfaces

Page 6 of 8 J Polym Res (2012) 19:9910

Fig. 4 P and VROP values of 12 miktoarm PEO-b-PMMA copoly-

mers induced by 18 kinds of surfaces at 400 K, respectively. The iso-

density surface pictures of PEO-b-PMMA induced by ci-882 surface

is displayed in subfigures a1, a2 by co-4432 surface, a3 by co-8832

surface, a4 by gra-2(888) surface, and a5 by rg-16168 surface; the iso-

density surface pictures of PEO-b-PMMA induced by ci-444 surface is

displayed in subfigures b1, b2 by co-448 surface, b3 by co-888 surface,

b4 by gra-888 surface, and b5 by rg-442 surface. Red represents PEO

component; green PMMA

Page 7: MesoDyn simulation study on the phase morphologies of miktoarm PEO-b-PMMA copolymer induced by surfaces

J Polym Res (2012) 19:9910 Page 7 of 8

23141 and 23241-type copolymer induced by co-4432

present negative values in VROP.

(6) The P and VROP values of co-4432, co-8832, gra-888,

gra-2(888) and rg-16168 display nearly the most high-

est in “co-4xx”, “co-8xx”, “gra-xxx”, “gra-2(xxx)” and

“rg-xxx” series surface except its inducing effect on

some copolymers. Therefore, the rougher the surface,

the higher the P and VROP value.

(7) The inserted iso-surface pictures is different from

our previous works. For the inducing effects of

doped nanoparticles in PEO/PMMA blends [15], PS-

b-PMMA copolymer [25] or PEO-b-PMMA copoly-

mer [28], the iso-surfaces were almost presented as

cubic phase morphologies. In addition, less cases dis-

played as lammellar phase morphologies for PEO/

PMMA blends [27] and PS-b-PMMA copolymer [26]

induced by surfaces. In contrast, the lammellar phase

morphologies has uniform interval distance between

layers.

Special miktoarm PEO-b-PMMA copolymer: 23141 and

23241-type

Owing to the dramatically high P data for 23141 and 23241-

type copolymers induced by surfaces, it is necessary to

investigate such special miktoarm PEO-b-PMMA copoly-

mer deeply. Owing to the same P, VROP and phase mor-

phologies of these two copolymers, we take the 23141-type

copolymer for example to discuss further.

We can detect the particularity in the architecture and

property of 23141-type copolymer, whose scheme is the

subfigure b3 in Fig. 1: firstly, the ratio of PEO to PMMA

block is 4:1, which has the highest PEO percentage of

Fig. 5 Iso-density surfaces of

23141-type PEO-b-PMMA

copolymer induced by 18

surfaces at 400 K. Redrepresents PEO component;

green PMMA

Page 8: MesoDyn simulation study on the phase morphologies of miktoarm PEO-b-PMMA copolymer induced by surfaces

Page 8 of 8 J Polym Res (2012) 19:9910

12 copolymers; secondly, each joint has two PEO blocks and

four PEO blocks in total, which could makes this copoly-

mer has much more opportunity to “meet” the same PEO

blocks, further form PEO-rich region; thirdly, the PMMA

block is flexible and lying in the middle of copolymer,

this can increase the “meeting opportunity” during adjusting

its placement and orientation; fourthly, the semicrystalline

nature of PEO could make it congregates easily, especially

at higher temperature such as 400 K.

Figure 5 displays the iso-density pictures induced by 18

surfaces at 400 K, respectively. We can seen the peculiar

microscopic phase separation clearly. The cases present

local phase separation due to the inducing effect of surfaces,

no matter what type of inducing surfaces.

Conclusions

We study about the phase morphologies of plain miktoarm

PEO-b-PMMA copolymers via MesoDyn simulation. It

shows that the values of P in the same group are the same at

400 K. The architecture of copolymers is the crucial factor

to determine the P values, but the chain length has little

relation with the P values.

We investigate the plain miktoarm PEO-b-PMMA

copolymers induced by 18 surfaces via mesoscopic simu-

lations. The simulation results show that introducing such

inducing surfaces is a good way of improving the degree of

order of the microscopic phases morphologies. No matter it

is a reinforcing or a weakening effect, the co-8832 and co-

4432 inducing surfaces exerts the top two most remarkable

influence on changing the phase morphologies of the mik-

toarm PEO-b-PMMA copolymers, except 23141 and 23241-

type copolymer. From the iso-surface pictures we can see

that the 23141 and 23241-type copolymers doped with no

matter which kind of inducing surfaces, they all present

special lamallae phase morphologies at 400 K, included its

plain copolymer.

Acknowledgements This work is supported by the Science-

Technology Foundation for Middle-Aged and Young Scientists of

Shandong Province (BS2010CL048), a Shandong Province Higher

School Science & Technology Fund Planning Project (J10LA61), and

a Zaozhuang Scientific and Technological Project (200924-2).

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