Biomedical Engineering Reference
In-Depth Information
4. Self-aggregation
Amphiphilic polyaspartamides composed of hydrophobic and hydrophilic groups
form nano-sized micellar aggregates, which have the structure of a hydrophobic
inner core and a hydrophilic shell, by self-assembly in aqueous solutions. The
driving force of aggregation is strong hydrophobic interactions with almost all
polymer aggregates having microdomains over one another. Either primary small
aggregates below 100 nm or secondary large aggregates over 100 nm can be
formed by self-assembly of amphiphilic graft copolymers based on
poly(aspartamide)s, given their stiff amide backbone structure, where the
secondary aggregate formation is caused by a kinetically-controlled process.[20]
Comb-type amphiphilic polymers with a flexible backbone favor primary
O
O
O
O
O
O
O
O
O
O
O
O
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
C
C
C
C
O
O
C
C
O
O
O
O
C
C
C
C
O
O
C
C
O
O
O
O
NH
NH
NH
NH
ONa
ONa
HN
HN
NH
2
NH
2
NH
(CH
2
)
6
NH
PCL-OH
NH
(CH
2
)
6
NH
PCL-OH
(CH
2
)
2
NH
(CH
2
)
2
NH
(CH
2
)
2
OH
(CH
2
)
2
OH
O
O
(CH
2
)
n-3
CH
3
(CH
2
)
n-3
CH
3
O
O
n=12, 16, 18
n=12, 16, 18
O
O
O
O
(CH
2
)
n-3
CH
3
(CH
2
)
n-3
CH
3
2
2
1
1
3
3
O
O
O
O
O
O
O
O
O
O
O
O
O
O
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
O
O
O
O
O
O
O
O
O
O
C
NH
C
NH
O
O
C
C
C
C
O
O
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
(CH
2
)
6
(CH
2
)
6
(CH
2
)
5
(CH
2
)
5
(CH
2
)
15
CH
3
(CH
2
)
15
CH
3
O
O
OH
OH
OH
OH
N
N
N
N
CH
CH
CH
CH
CH
CH
CH
CH
n
n
N
N
CH
CH
CH
3
CH
3
N
N
CH
CH
4
4
6
6
5
5
Fig. 5. Chemical structure of various amphiphilic polyaspartamides (1: akylchain-g-poly(aspartic
acid); 2: PCL-g-poly(asparagine); 3: PLA-g-PHEA; 4: C18/MPEG/API-g-polyaspartamide; 5:
API-g-poly(asparagine); 6: poly(
N
-subsituted
ŋ
/
Ȳ
asparagines).
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