Chinese Chemical Letters
journal homepage: www.elsevier.com/locate/cclet
Original article
Synthesis of novel copolymer: Poly(p-dioxanone-co-
L-phenylalanine)
a,b
a,b
a
a
c
a,
Bing Wang , Chi Ma , Zuo-Chun Xiong , Cheng-Dong Xiong , Quan-Hua Zhou , Dong-Liang Chen *
a
Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, China
b
University of Chinese Academy of Sciences, Beijing 100049, China
c
Sichuan Staff University of Science and Technology, Chengdu 610041, China
A R T I C L E I N F O
A B S T R A C T
Article history:
In order to expand the application of poly(p-dioxanone) or PPDO in biomedical area, a series of novel
copolymers were synthesized successfully by one-step, melted copolymerization of p-dioxanone (PDO)
Received 26 December 2012
Received in revised form 2 February 2013
Accepted 26 February 2013
Available online 12 April 2013
and L-phenylalanine N-carboxyanhydride (L-Phe-NCA) monomers. With the in-feed molar ratio of L-Phe-
1
NCA/PDO equal to 1/20, the conversions of the two kinds of monomers were calculated from H NMR.
The average molecular weight and polydispersity of the copolymer increase with the increasing reaction
time and catalyst concentration. However, the conversions of the two kinds of monomers did not change
Keywords:
1
with the reaction conditions. A three-step mechanism is presented and proved by high resolution
NMR and IR spectrums.
H
Copolymer
p-Dioxanone
ß 2013 Dong-Liang Chen. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights
L
-Phenylalanine
reserved.
Mechanism
1
. Introduction
In this work, copolymers of poly(p-dioxanone-co-
nine) were synthesized using different polymerization conditions
by a one-step, melted reaction of PDO and -phenylalanine N-
carboxyanhydride ( -Phe-NCA). A three-step mechanism was
provided and proven by FTIR and H NMR.
L-phenylala-
Poly(p-dioxanone) (PPDO), as an aliphatic polyester, has been
L
used in biomedical applications, such as tissue engineering, bone
fracture fixation and controlled drug delivery, due to its
outstanding biodegradability, biocompatibility and flexibility [1–
L
1
5
]. However, the combination of high crystallinity, intrinsic
2. Experimental
hydrophobicity of PPDO and the absence of biological properties
have limited its further application [6]. The most frequently used
method to improve the performances of PPDO, such as crystallinity
and hydrophobicity of PPDO, is copolymerization [7–12].
2
.1. Synthesis of L-Phe-NCA [17]
The
L-Phe-NCA was synthesized from L-Phe (5.0 g) and
In recent years, functionalized polyesters, especially polyesters
triphosgene (3.7 g) in dry THF (50 mL) at 50 8C for 4 h under N
2
containing
a-amino acid, have attracted much attention. Many
atmosphere. After completion of the reaction, the mixture was
concentrated by rotary evaporator at 30 8C and dry hexane was
added to precipitate the crude product. The crude product was
papers have reported on the synthesis of
a
-amino acid containing
polyesters and revealed that, as copolymerization components,
amino acids could alter not only the physical properties, but also
the biological properties of polyesters [13]. However, there have
been only a limited number of published reports regarding the
copolymers of p-dioxanone (PDO) and amino acids [14] and
therefore, the aim of our research was to synthesize copolymers
purified by recrystallization from diethyl ether/hexane (1/2, v/v)
1
twice to yield
L
-Phe-NCA monomer of high purity. H NMR
(
(
300 MHz, CDCl
m, 1H, CH), 2.94–3.35 (m, 2H, CH
3
): d 7.19–7.41 (m, 5H, ArH), 5.60 (s, 1H, NH), 4.55
ꢀ
1
2
). FTIR (KBr, cm ): n 3351 (N–
H), 3031 (C–H from phenyl), 2905 (C–H), 1849 (C 55 O), 1779 (C 55 O).
.2. Synthesis of poly(p-dioxanone-co- -phenylalanine)
composed of PDO and
L-phenylalanine (L-Phe) by a new,
convenient method. -Phe was chosen as the copolymerization
L
2
L
component because its rigid benzyl group may alter the flexibility
of the copolymer chains and decrease the crystallinity, along with
specific inhibitions on cell proliferation [15,16].
To a 100-mL round-bottom flask containing PDO (5.0 g),
calculated quantities of -Phe-NCA and stannous octoate were
L
added. The flask was sealed using a long-neck piston connected
to an oil pump to remove moisture, oxygen, and solvent until
ꢀ3
*
the pressure was reduced to below 10 Pa. The polymerization
was carried out under vacuum at 95 8C with magnetic stirring.