Synthesis and self-assembly of amphiphilic and biocompatible poly(vinyl alcohol)-block-poly(L-lactide) copolymer

Article abstract of DOI:10.1016/j.polymer.2016.08.005

Well-defined amphiphilic and biocompatible poly(vinyl alcohol)-block-poly(L-lactide) copolymers (PVA-b-PLLA) were synthesized by the combination of reversible addition-fragmentation chain transfer (RAFT), ring opening polymerization (ROP), and click chemistry. First, an innovative azide-functionalized xanthate mediated chain transfer agent (CTA) [S-(3-azidopropyl propanamide)-(O-butyl xanthate)] was synthesized and used for vinyl acetate (VAc) polymerization through RAFT. Then, azide-terminated poly(vinyl acetate) (azide-PVAc) was converted to the corresponding azide-terminated poly(vinyl alcohol) (azide-PVA) through hydrolysis. Alkyne-terminated poly (L-lactide) (alkyne-PLLA) was synthesized via ROP using a bifunctional initiator, having an alkyne and a hydroxyl group. Finally, azide-PVA and alkyne-PLLA were coupled by 1,3 cycloaddition click reaction to get PVA-b-PLLA. Synthesized azide-PVAc, azide-PVA, alkyne-PLLA and PVA-b-PLLA were characterized by size exclusion chromatography and ¹H NMR spectroscopy. The self-assembly of PVA-b-PLLA in water was investigated by transmission electron microscope, atomic force microscopy, dynamic light scattering and ¹H NMR spectroscopy. Spherical micelles in water were clearly observed. The critical micelle concentration of PVA-b-PLLA in water was determined by fluorescence spectroscopy, and it was decreased with increasing the molecular weight of PLLA block. PVA-b-PLLA exhibited low cytotoxicity which could be used in biomedical application.

Full text of DOI:10.1016/j.polymer.2016.08.005

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Polymer 100 (2016) 28e36
Contents lists available at ScienceDirect
Polymer
journal homepage: www.elsevier.com/locate/polymer
Synthesis and self-assembly of amphiphilic and biocompatible
poly(vinyl alcohol)-block-poly( -lactide) copolymer
L
Avnish Kumar Mishra, Jicheol Park, K.L. Vincent Joseph, Sandip Maiti, Jongheon Kwak,
Chungryong Choi, Seung Hyun, Jin Kon Kim*
National Creative Research Initiative Center for Smart Block Copolymers, Department of Chemical Engineering, Pohang University of Science and
Technology, Pohang, Kyungbuk 790-784, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Well-defined amphiphilic and biocompatible poly(vinyl alcohol)-block-poly(L-lactide) copolymers (PVA-
Received 28 June 2016
Received in revised form
23 July 2016
Accepted 2 August 2016
Available online 3 August 2016
b-PLLA) were synthesized by the combination of reversible addition-fragmentation chain transfer (RAFT),
ring opening polymerization (ROP), and click chemistry. First, an innovative azide-functionalized
xanthate mediated chain transfer agent (CTA) [S-(3-azidopropyl propanamide)-(O-butyl xanthate)]
was synthesized and used for vinyl acetate (VAc) polymerization through RAFT. Then, azide-terminated
poly(vinyl acetate) (azide-PVAc) was converted to the corresponding azide-terminated poly(vinyl
alcohol) (azide-PVA) through hydrolysis. Alkyne-terminated poly (L-lactide) (alkyne-PLLA) was synthe-
Keywords:
Poly(vinyl alcohol)-block-poly(L-lactide)
copolymers
Azide-functionalized RAFT initiator
Amphiphilic and biocompatible materials
sized via ROP using a bifunctional initiator, having an alkyne and a hydroxyl group. Finally, azide-PVA and
alkyne-PLLA were coupled by 1,3 cycloaddition click reaction to get PVA-b-PLLA. Synthesized azide-PVAc,
azide-PVA, alkyne-PLLA and PVA-b-PLLA were characterized by size exclusion chromatography and 1H
NMR spectroscopy.
The self-assembly of PVA-b-PLLA in water was investigated by transmission electron microscope,
atomic force microscopy, dynamic light scattering and 1H NMR spectroscopy. Spherical micelles in water
were clearly observed. The critical micelle concentration of PVA-b-PLLA in water was determined by
fluorescence spectroscopy, and it was decreased with increasing the molecular weight of PLLA block.
PVA-b-PLLA exhibited low cytotoxicity which could be used in biomedical application.
© 2016 Elsevier Ltd. All rights reserved.
1. Introduction
[13e17]. As a result, PVA has been extensively used in various ap-
plications such as crosslinking [18], making gels, nano composite
Well-defined amphiphilic, biocompatible block copolymers
have many potential application such as nanocarriers of thera-
peutic drugs [1e4], genes [5], bioactive molecules [5], and diag-
nostic applications [6], for their improved water solubility, and
extended blood circulation duration [5]. Amphiphilic block co-
polymers have been also extensively used for antibiofouling [7],
nanoparticle synthesis, and colloidal stabilization [8e11]. Gener-
ally, nonionic amphiphilic block copolymers consisting of hydro-
philic block, for instance, polyethylene oxide and poly(N-vinyl
pyrrolidone) are not biodegradable. On the contrary, poly(vinyl
alcohol) (PVA) degrades in environmental and in vivo conditions
[12]. Also, it shows solubility in water at wide temperature range,
and it prevents nonspecific protein adsorption in biological systems
[16], nano-fiber, hybrid nanofiber [19] and metal nanoparticles
[20e24]. PVA is typically obtained by hydrolysis of poly(vinyl ace-
tate) (PVAc), which is synthesized by radical polymerization due to
the high reactivity of vinyl acetate monomer [25]. There are several
methods to explore for the controlled synthesis of PVA homopol-
ymer and PVA-containing block copolymers, for instance, PVA-
block-polystyrene copolymer (PVA-b-PS) [25,26], PVA-block-poly(-
methylmethacrylate) copolymer (PVA-b-PMMA) [27,28], PVA-
block-poly(vinylacetate) copolymer (PVA-b-PVAc) [17,29], and PVA-
block-poly(ε-caprolactone) copolymer (PVA-b-PCL) [30,31].
On the other hand, hydrophobic poly(L-Lacide) (PLLA) has
excellent biocompatibility and biodegradability approved by the
FDA for biomedical applications in humans [1]. Also, PLLA con-
taining block copolymer micelles have been widely employed as a
drug delivery system due to their stability in vivo condition [26].
The synthesis of amphiphilic and biocompatible PVA-b-PCL [27,28]
and PVA-g-PCL [29e31] was already reported in the literature, but
* Corresponding author.
E-mail address: jkkim@postech.ac.kr (J.K. Kim).
http://dx.doi.org/10.1016/j.polymer.2016.08.005
0032-3861/© 2016 Elsevier Ltd. All rights reserved.

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A.K. Mishra et al. / Polymer 100 (2016) 28e36
29
PCL has some drawbacks compared of PLLA, such as low glass
transition temperature and less biodegradable properties [26].
Also, although the synthesis and self-assembly of amphiphilic
poly(vinyl alcohol)-graft-oligo(lactide) copolymer (PVA-g-OLLA)
was reported [32,33], well defined PVA-block-PLLA copolymer with
lower molecular weight distribution would be preferred but to
obtain uniform size distribution of micelles for delivery of hydro-
phobic drugs as well as the synthesis of biocompatible metal
nanoparticles.
Since PVA should be synthesized by the hydrolysis of PVAc, PLLA
can easily degrade during hydrolysis under acidic or basic condi-
tion. To prevent degradation of PLLA during the hydrolysis of PVAc
block in PLLA-b-PVAc, in this study, we used “click chemistry”.
First, azide-terminated PVAc with narrow polydispersity were
synthesized by using xanthate mediated reversible addition-
fragmentation chain transfer (RAFT) polymerization [34,35] with
400 at room temperature in CDCl3, dimethyl sulfoxide-d6 (DMSO-
d6), and D2O as solvent. Vinyl acetate monomer conversion (%) was
determined from 1H NMR spectroscopy in CDCl3 by comparing the
integrated peak area of the residual vinylic signals at 4.5 ppm (1H)
of the monomer with the combined peak area of remaining vinylic
signals at 4.8 ppm (1H) and the protons adjacent to acetate group at
4.5e4.9 ppm (1H) of the corresponding polymer. The molecular
weight of the alkyne-terminated PLLA homopolymer was deter-
mined from 1H NMR spectrum in DMSO-d6 by comparing the in-
tegrated peak intensity of aliphatic methylene protons of the
backbone PLLA at ~5.2 ppm (1H) to that of methyl and methylene
protons of the polymer chain-end at 4.1e4.25 ppm (3H).
The polydispersity index (PDI ¼ Mw/Mn) of all samples was
measured by size exclusion chromatography (SEC: Waters 2414
refractive index detector) with two 300 mm (length) ꢀ 7.5 mm
(inner diameter) columns including particle size of 5
mm (PLgel
a
newly synthesized S-(3-azidopropyl propanamide)-(O-butyl
5 mm MIXED-C: Polymer Laboratories) with dimethylformamide
xanthate) (APPBX) chain transfer agent (CTA). It is noted that the
ester group containing azide-terminated xanthate initiator cannot
be used for the synthesis of azide-terminated PVA via hydrolysis of
azide-terminated PVAc, because the azide chain end is not stable
under basic condition due to the presence of the ester group.
Although some research groups have used azide-terminated CTA
with benzyl group for the synthesis of PVAc, the synthesized PVAc
showed broad molecular weight distribution (polydispersity index
(PDI) > 1.4) [27,36]. This is because CTA with benzyl group inhibits
the polymerization of VAc due to the formation of highly stable
radicals from benzyl group [37,38]. Next, alkyne-terminated PLLA
(alkyne-PLLA) was synthesized by ring opening polymerization
(ROP) using a bifunctional initiator bearing an alkyne and hydroxyl
group. Finally, azide-PVAc and alkyne-PLLA were coupled by 1,3
cyclo addition reaction so called as “click chemistry” to produce
PVA-b-PLLA. Azide-PVA, alkyne-PLLA, and PVA-b-PLLA with
various molecular weights and block compositions were charac-
terized by size exclusion chromatography (SEC) and 1H NMR
spectroscopy.
(DMF) as an eluent, and a flow rate of 1 mL/min at 32 ꢁC. The col-
umns were calibrated against PS standard samples (Polymer Lab).
TEM images were obtained by using S-7600 Hitachi trans-
mission electron microscope operating at an acceleration voltage of
80 kV. The TEM samples were prepared by dipping the carbon-
coated copper grid into the aqueous block copolymer solution
(1 mg/mL) followed by the removal of extra solution with a filter
paper. Atomic force microscopy (AFM, Digital Instrument) was used
to observe the micelles of block copolymer in water solution.
Fluorescence measurements were carried out by using a JASCO
Fluorescence Spectrometer [39]. Aqueous PVA-b-PLLAs solutions
with various concentrations from 2 ꢀ 10ꢂ4 to 1 mg/mL were pre-
pared in water. The stock solution of pyrene in acetone was trans-
ferred in a series of 5 mL vials and acetone was evaporated
overnight. Then, the block copolymer solutions were added to the
vials to get a final pyrene concentration of 7 ꢀ 10ꢂ7 M in each vial.
The excitation spectra (300e360 nm) of the solutions were recor-
ded at an emission wavelength of 394 nm using a slit width of
2.5 nm. The peak intensities ratio of the excitation spectra of pyrene
at 337 nm (I337) and 334 nm (I334) was plotted as a function of
polymer concentration. The critical micelle concentration (cmc)
was obtained as the interception of the two straight lines at lower
and higher concentrations. A dynamic light scattering (DLS)
experiment was performed to determine the micelle size of PVA-b-
PLLA in aqueous solution at 25 ꢁC. Aqueous polymeric solutions
The self-assembly of PVA-b-PLLA in water was investigated by
transmission electron microscopy (TEM) and dynamic light scat-
tering (DLS). The critical micelle concentration (cmc) of PVA-b-PLLA
in water was determined by fluorescence spectroscopy. PVA-b-
PLLA exhibited low cytotoxicity which could be used in biomedical
application.
were filtered through 0.45 mm filter.
2. Experimental
2.3. Synthesis of 3-azidopropan-1-amine (1)
2.1. Materials
In a 500 mL two neck flask, 1-chloro-3-aminopropane hydro-
chloride (0.19 mol, 25 g) was dissolved in 125 mL of water, followed
by dropwise addition of NaN3 (0.6 mol, 40 g) in 200 mL of water.
The reaction mixture was heated to reflux at 110 ꢁC for overnight,
followed by removal of 70% of water on a rotary evaporator. The
resulting mixture was cooled in an ice bath and 300 mL of diethyl
ether was added to it. Then, KOH pellets (50 g) were added at low
temperature (<10 ꢁC). The organic layer was separated and the
aqueous phase was extracted with diethyl ether (2 ꢀ 300 mL). The
combined organic layers were dried over K2CO3 and concentrated.
Finally,16.35 g of clear yellow oil (yield: 86%) product was obtained.
1-chloro-3-aminopropane hydrochloride (Aldrich, St Louis, USA,
99%), triethylamine, sodium azide (Aldrich, St Louis, USA, 99%), 2-
bromopropionyl bromide (Aldrich, St Louis, USA, 97%), 1,8-
Diazabicyclo[5.4.0]undec-7-ene) (DBU) (Aldrich, St Louis, USA,
98%), diethyl ether (Samchun pure Chemical, Korea), hexane
(Samchun pure Chemical, Korea), methanol, (Samchun pure
Chemical, Korea), Diethylether (Samchun pure Chemical, Korea),
anhydrous magnesium sulfate (Samchun pure Chemical, Korea)
were used as received. Vinyl acetate (VAc) (Aldrich, St Louis, USA,
98%) was dried over CaO and then distilled under reduced pressure.
(
L
-lactide) (LLA) (Aldrich, St Louis, USA, 99%) was recrystallized
1H NMR (400 MHz, CDCl3)
d [ppm] [Fig. S1]: 3.05 (t, eCH2N3),
from ethyl acetate. 2, 20 azobis(isobutyronitrile) (AIBN) was
recrystallized from methanol. Column chromatography was con-
2.48 (t, eCH2NH2), 1.41 (m, eCH2e), 1.12 (s, eNH2). 13C NMR
(400 MHz, CDCl3)
d [ppm]: 32.2 (eCH2e) 39.1 (eCH2eNH2), 48.9
ducted with silica gels (Merck silica gel 60, mesh size 0.2e0.5
mm).
(eCH2eN3).
2.2. Characterizations
2.4. Synthesis of N-(3-azidopropyl)-2-bromopropanamide (2)
1H NMR spectra were recorded on Bruker digital Avance III
In a dried and N2 purged round-bottom flask, 10 g (0.1 mol) of 3-

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30
A.K. Mishra et al. / Polymer 100 (2016) 28e36
azidopropan-1-amine and 15.4 mL (0.11 mol) of triethylamine were
added in 100 mL of dry THF with constant stirring under N2 at-
mosphere until clear solution was observed. After that, 23.3 g
(0.108 mol) of 2-bromopropionyl bromide was added drop wise to
the above solution under ice cooled condition. The reaction mixture
was stirred for 48 h at room temperature, and the obtained residue
(i.e., Et3N$HBr) was filtered and the filtrate was evaporated. The
resulting solid was dissolved in ethyl acetate and washed thor-
oughly with 5% sodium bicarbonate (4 ꢀ 100 mL) and brine
(4 ꢀ 100 mL). The organic layer was further washed with water
(4 ꢀ 150 mL), dried over anhydrous MgSO4 and filtered. The filtrate
was concentrated to give 22 g of clear yellow oil (yield: 93%).
the polymerization mixture was used to determine the monomer
conversion by 1H NMR. The rest of the crude mixture was dissolved
in 20 mL THF, precipitated from 350 mL hexane and dried under
vacuum at room temperature for 24 h. Monomer conversion was
85% determined by 1H NMR.
1H NMR (400 MHz, DMSO-d6)
d [ppm] [Fig. 1A]: 3.25e3.42 (m,
eCH2N3e and CH2NH with residual water), 1.6e1.8 (m, eCH2CH
(OCOCH3) eCH (CH3), eCH2 CH2 CH2e, eCH2 CH2 NHe), 4.5e4.6
(m, eCH (CH3) e, eCH2OC(S) S e), 4.70e4.98 (m, eCH2CH
(OCOCH3) 7. 8 (s, eNH). 0.99e1.45 (m, e CH2CH3e, eCH3), Mn
(NMR) ¼ 21,000 g molꢂ1, PDI (SEC) ¼ 1. 22.
1H NMR (400 MHz, CDCl3)
d
[ppm] [Fig. S2]: 3.22e3.29 (m,
2.8. Typical synthesis of azide-terminated poly (vinyl alcohol)
(Azide-PVA) (5) (run 5a, Table 1)
eCH2N3e and CH2NH), 1.69e1.73 (m, eCH (CH3) Bre and eCH2e),
4.3e4.4 (q, eCH (CH3) Br e), 7.18 (s, eNH). 13C NMR (400 MHz,
CDCl3)
d
[ppm]: 48.9 (eCH2N3e), 28.3 (eCH2e) 37.4 (eCH2NH),
A methanol solution (40 mL) of potassium hydroxide (1 g, 75 wt %
of azide-terminated PVAc) was added to the methanol solution
(80 mL) of azide terminated PVAc (1.5 g) and the mixture was stirred
at room temperature for 3 h. After the reaction, the precipitate was
filtered. The obtained residue was washed by methanol three times
and by ether twice to get purified azide-terminated PVA.
170.1 (eCOe), 44.2 (eCHe), 22.3 (eCH3e).
2.5. Synthesis of potassium O-butyl xanthate (20)
Potassium O-butyl xanthate was prepared according to the
literature [40]. In brief, 5.63 g (0.1 mol) of KOH was added in 60 mL
(0.682 mol) of butanol-1 and stirred to get clear solution. Then,
20 mL (0.332 mol) of CS2 was added slowly to the above solution
during stirring and the resultant solution was stirred for overnight.
It was suspended in 400 mL ether and filtered. The precipitate was
washed thrice with ether and dried under vacuum at room tem-
perature for overnight.
1H NMR (400 MHz, DMSO-d6)
d [ppm] [Fig. 1B]: 3.25e3.42 (m,
eCH2N3e and CH2NH with residual water), 1.2e1.7 (m, eCH2CH
(OH) eCH (CH3), eCH2 CH2 NHe), 4.1e4.8, eCH (CH3) e, eCH2CH
(OH), 3.65e4.02 (m, eCH2CH (OH), 7. 78 (s, eNH). 0.99 d, eCH3), Mn
(NMR) ¼ 11,500 g molꢂ1, PDI (SEC) ¼ 1.21.
2.9. Synthesis of alkyne-terminated poly(L-lactide) (6)
1H NMR (400 MHz, Acetone-d)
d [ppm]: 4.3 (t, eCH2S(CO)S),1.60
(m, e S(CO)SCH2CH2-), 1.39 (m, eCH2CH3e), 0.9 (t, eCH3).
Alkyne-terminated poly(
thesized via metal free ROP of
initiator and 1,8- diazabicycloundec-7-ene (DBU) as a catalyst. In a
L
-lactide) (Alkyne-PLLA-OH) was syn-
D,L-lactide using 4-pentyn-1-ol as
2.6. Synthesis of 3 S-(3-azidopropyl propanamide)-(O-butyl
xanthate) [(APPBX (3)]
typical experiment (run 6a, Table 1),
3
g
of
L-lactide
(2.08 ꢀ 10ꢂ2 mol) was placed in a 100 mL dry round bottle flask
In a dried and nitrogen purged round-bottom flask, 5.22 g
(2.22 ꢀ 10ꢂ2 mol) of N-(3-azidopropyl)-2-bromopropanamide was
dissolved in 30 mL of acetone and stirred under nitrogen atmo-
sphere. After that, 8.39 g (4.44 ꢀ 10ꢂ2 mol) of potassium-O-butyl
xanthate in 30 mL acetone solution was added drop wise. The re-
action mixture was stirred for 24 h at room temperature. The
precipitated byproduct was removed by filtration and the filtrate
was evaporated to dryness. The residue was dissolved in ethyl ac-
etate and washed thoroughly with brine (4 ꢀ 100 mL). The organic
layer was further washed with water (4 ꢀ 150 mL), dried over
anhydrous MgSO4, and filtered. The filtrate was concentrated to
give 4.95 g of clear yellow oil (yield: 73%).
equipped with a magnetic bar under nitrogen atmosphere in globe
box. Then, 39
m
L of 4- pentyn-1-ol (0.35 g, 4.17 ꢀ 10ꢂ4 mol) and
15
m
L (0.015 g, 5.85 ꢀ 10ꢂ5 mol, 0.5% w/w ratio of lactide) of DBU
were added to the flask. The polymerization was carried out at
25 ꢁC for 30 min and stopped by freezing the reaction mixture with
liquid N2. The crude product was dissolved in 2 mL of dichloro-
methane (DCM) and precipitated from 200 mL of ether, then
filtered. This purification method was repeated three times. Finally,
solid product was vacuum dried at room temperature for 24 h.
Monomer conversion was checked gravimetrically (~99%). Polymer
yield ¼ 2.95 g.
1H NMR (400 MHz, DMSO-d6)
d [ppm] [Fig. 1C]: 2.8 (s, eCCH),
1H NMR (400 MHz, CDCl3)
d
[ppm] [Fig. S3]: 3.25e3.35 (m,
2.2 (t, eCCH2e), 1.75 (q, eCH2CH2CH2e), 1.45 (m, eCHCH3e), 5.2 (q,
eCHCH3e), 4.1e4.3 (m, eCHCH3eOH, eCH2OCOe), 1.2e1.3 (d,
eCHCH3eOH), Mn (NMR) ¼ 4200 g molꢂ1, PDI(SEC) ¼ 1.07.
eCH2N3e and CH2NH),1.51 (d, eCH (CH3)),1.70e1.80 (m, eCH2 CH2
CH2e and eCH2 CH2 NHe), 4.2e4.3 (q, eCH (CH3) e), 4.54 (q,
eCH2OC(S) S e), 6.58 (s, eNH). 1.36e1.41 (m, e CH2CH3), 0.91 (t,
eCH3), 13C NMR (400 MHz, CDCl3)
d
[ppm]: 48.1 (eCH2N3e), 28.7
2.10. Click reaction between Azide-PVA and Alkyne-PLLA (7)
(eCH2CH2NHe) 37.4 (eCH2NH), 170.1 (eNHC(O)e), 49.37 (eCHe),
19.2 (eCH3CH), 213.9 (eOC(S)Se), 74.9 (eOC(S)SCH2e), 30.3
(eOCH2CH2e), 16.6 (eCH2CH3), 13.7 (eCH3).
PVA-b-PLLA was synthesized via click reaction using Cu(I)Br and
N,N,N0,N',N00-pentamethyldiethylenetriamine (PMDETA). In
a
typical reaction (run 7a, Table 2), the mixture of CuBr (20 mg,
0.11 mmol), Azide-PVA homopolymer (0.2 g, Mn(NMR) ¼ 11,500,
0.016 mmol), alkyne-PLLA homopolymer (0.9 g, 0.02 mmol),
2.7. Typical synthesis of azide-terminated poly (vinyl acetate)
(Azide-PVAc) (4) (run 4a, Table 1)
PMDETA (23 mL, 0.11 mmol), and DMSO (6 mL) was put into a tube
In a dried and nitrogen purged polymerization tube, 2.5 mL
(2.71 ꢀ 10ꢂ2 mol) of VAc, 27.5 mg (9.04 ꢀ 105 mol) of APPBX (3),
and 3 mg (1.8 ꢀ 10ꢂ5 mol) of AIBN were added in 2.5 mL dichlo-
roethane (DCE). The homogeneous solution was degassed under
nitrogen for 45 min. The polymerization tube was immersed in a
preheated oil bath at 62 ꢁC for 24 h. The reaction was stopped by
freezing the reaction mixture in liquid nitrogen. A tiny portion of
and purge nitrogen for 45 min. Then, the tube was immersed in a
preheated oil bath at 45 ꢁC for 20 h. The solution was twice
precipitated in diethyl ether/chloroform/methanol (4:1:1, v/v)
mixture solvents to remove copper and unreacted PLLA homopol-
ymer. The precipitate was re-dissolved in DMSO and dialyzed in
aqueous solution with ethylene diamine tetraacetic acid disodium
salt (0.2% wt/v) to remove the residual copper and unreacted PVA

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A.K. Mishra et al. / Polymer 100 (2016) 28e36
31
Fig. 1. 1H NMR spectra of (A) azide-PVAc244, (B) azide-PVA244 and (C) alkyne-PLLA30 in DMSO-d6 at room temperature.
Table 1
Characteristics of Synthesized azide-PVAc, azide-PVA and alkyne-PLLA homopolymers.
Run
Homopolymersa
Monomer (equiv.)
Reaction time (h)
Conv. (%) (NMR)
Mn (NMR)
PDIb (SEC)
4a
4b
4c
5a
5b
5c
6a
6b
azide-PVAc244
azide-PVAc116
azide-PVAc70
azide-PVA224
azide-PVA116
azide-PVA70
300
150
80
e
12.0
8.0
5.0
3
3
3
82
97
96
99
99
99
99
99
21,000
10,000
6100
11,500
5300
3500
4200
7000
1.22
1.17
1.10
1.21
1.19
1.16
1.07
1.09
e
e
alkyne-PLLA30
alkyne-PLLA51
35
70
0.5
0.5
a
Number represents the degree of polymerization (DP) calculated by using 1H NMR.
Determined by SEC (1 mL/min, 32 ꢁC) calibrated based on PS standards in DMF.
b