Comparative study on post-polymerization modification of C1 poly(benzyl 2-ylidene-acetate) and its C2 analog poly(benzyl acrylate)

Article abstract of DOI:10.1002/pola.27891

The present study investigates the challenging approach of post-polymerization modification on polymers with a sterically demanding reaction center. Therefore, the general possibility to functionalize polymethylene moieties was investigated. Poly(benzyl 2-ylidene-acetate) was synthesized by polymerization of benzyl 2-diazoacetate utilizing [(L-prolinate)Rh^I(1,5-dimethyl-1,5-cyclooctadiene)] as a catalyst. Subsequently, the modification of C1 polymerized poly(benzyl 2-ylidene-acetate) with amines was analyzed and the obtained data set was compared with experimental data derived for the C2 analog poly(benzyl acrylate). This is the first study on post-polymerization modification utilizing densely functionalized polymethylenes as starting materials.

Full text of DOI:10.1002/pola.27891

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Comparative Study on Post-Polymerization Modification of C1
Poly(benzyl 2-ylidene-acetate) and Its C2 Analog Poly(benzyl acrylate)
Tim Krappitz, Patrick Theato
Department of Chemistry, Institute for Technical and Macromolecular Chemistry, University of Hamburg,
Hamburg D-20146, Germany
Correspondence to: P. Theato (E-mail: theato@chemie.uni-hamburg.de)
Received 10 June 2015; accepted 25 August 2015; published online 25 September 2015
DOI: 10.1002/pola.27891
ABSTRACT: The present study investigates the challenging
approach of post-polymerization modification on polymers
with a sterically demanding reaction center. Therefore, the gen-
eral possibility to functionalize polymethylene moieties was
investigated. Poly(benzyl 2-ylidene-acetate) was synthesized by
polymerization of benzyl 2-diazoacetate utilizing [(L-prolina-
data set was compared with experimental data derived for the
C2 analog poly(benzyl acrylate). This is the first study on post-
polymerization modification utilizing densely functionalized
C
V
polymethylenes as starting materials. 2015 Wiley Periodicals,
Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 686–691
te)RhI(1,5-dimethyl-1,5-cyclooctadiene)] as
a catalyst. Subse-
KEYWORDS: amidation; C1 polymerization; functionalization of
polymers; post-polymerization modification; polymethylenes;
syndiotactic; synthesis
quently, the modification of C1 polymerized poly(benzyl 2-
ylidene-acetate) with amines was analyzed and the obtained
invented by Shea et al. in 1997.6 This technique is highly
interesting with respect to the living polymerization charac-
ter and the variability of end groups. However, the synthetic
access toward functional sulfoxide ylides remains highly
challenging. Many other ylide structures have either not yet
been investigated or did not lead to polymeric materials and
remained unpublished.7,8 Another approach is based on
transition metal catalyzed polymerization of a-diazocarbonyl
compounds as monomers, which was mainly influenced
by the research groups of Liu, Ihara, and de Bruin
(Scheme 1).9–11
INTRODUCTION Ever since Staudinger1 devised the term
polymer analogues reaction in 1939, post-polymerization
modification got recognized as a powerful synthetic toolbox
in polymer science and developed into a widely used ap-
proach to vary the functionalities of polymeric materials.2
However, up to date, little to no research has been conducted
on polymethylenes with densely packed side chain function-
alities. This is mainly attributed to difficulties in conventional
polymerization techniques to synthesize the appropriate
polymethylenes. Conventional polymerization techniques
usually suffer from limitations arising from higher function-
alities on monomers, for example, due to catalyst poisoning.3
Various approaches were tested to synthesize polyolefins
functionalized with an ester- or acid group attached to every
main chain carbon atom. However, facile radical homopoly-
merization, for example, of maleic anhydride is not suitable,
and hence numerous attempts following classic approaches
were made.4 There is one exception, a recent example of
While, all research groups make use of a-diazocarbonyl com-
pounds as monomers, the investigated catalytic systems,
based on copper, palladium, and rhodium perform tremen-
dously different. Many of the investigated catalysts result in
a lack of control of the resulting polymethylene backbones
and their molecular weight. Palladium catalysts often result
in polymers containing azo-groups in their backbone
besides the desired polymethylene repeating unit.12 In 2006,
de Bruin et al. developed a polymerization technique of a-
diazocarbonyl compounds via rhodium catalyst mediation.11
This approach results in well defined syndiotactic poly-
methylenes, marking a turn in carbene polymerization as it
is the first example of stereoregular carbene polymeriza-
tion.13 Furthermore, no ill-defined repeating units were
noticed, that is, no presence of azo-groups. By far, this
€
Mullen et al. shows the feasibility of this route to synthesize
poly(methylene amine), utilizing 1,3-diacetyl-4-imidazolin-2-
one as a monomer.5 For the first time, they succeeded in the
synthesis of a polymer containing an amino group at each
carbon atom of the polymer backbone. Recently, densely
functionalized polymethylenes got accessible via novel C1
polymerization techniques, such as trialkylborane-mediated
living polyhomologation of sulfoxide ylides, which was
Additional Supporting Information may be found in the online version of this article.
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Fourier transform infrared (FT-IR) spectroscopy was meas-
ured on a Thermo Scientific Nicolet iS10. Measurements
were conducted with an attenuated total reflectance (ATR)
attachment. Nuclear magnetic resonance (NMR) spectra were
recorded on a Bruker 300 MHz FT-NMR spectrometer in
deutorated solvents. Size exclusion chromatography (SEC)
data were obtained from two setups: (1) Intelligent pump
JASCO PU-980, RI detector SFD RI 2000, Linear 5 lm column
MZ-Gel SDplus calibrated with polystyrene standards. Chloro-
form was used as eluent. (2) SEC setup using tetrahydrofur-
ane as eluent consisted of FLOM Intelligent Pump Al-12-13,
SFD RI 2000 detector, one guard column PLgel 10 lm and
two PLgel 10 lm MIXED-B columns. For calibration linear
polystyrene standards with various molecular weights were
used. Thermogravimetric analysis (TGA) was performed on a
Mettler Toledo TGA 1 Star System under air. Differential
scanning calorimetry was done on a DSC 1 Star System. For
static light scattering (SLS) analysis an ALV/CSG-3 Compact
Goniometer was used together with an ALV/LSE-5003 Multi-
ple Tau Digital correlator. Measurements of the refractive
index increments were conducted on a DnDc-2010 differen-
tial refractometer.
SCHEME 1 Illustrating the general approach of C1 polymeriza-
tion utilizing a-diazocarbonyl compounds as monomers. [Color
figure can be viewed in the online issue, which is available at
wileyonlinelibrary.com.].
approach results in the highest molecular weights published
on C1 polymers via transition metal catalysis. With respect
to the investigated monomer scope of C1 polymerization
techniques, benzyl 2-diazoacetate and ethyl 2-diazoacetate
have been most frequently used and polymers were obtained
in good yields and high molecular weights, that is, 85% yield
and 590000 g/mol (Mw) for poly(ethyl 2-ylidene-acetate).14
Polyolefins and their structural analogues polymethylenes,
originating from carbene precursors as monomers, are highly
important polymeric materials. However, up to now it still
remains an elusive goal to account for the need of various
densely packed side chain functionalities by classic
approaches and even by C1 polymerization as their mono-
mer scope is not yet fully explored. Consequently, post-
polymerization modification might help to solve the current
limitation for monomer functionalities, simply by applying
click chemistry modification tools to C1 polymers and/or
their respective monomers. However, up to now, the investi-
gated polymethylene side chains are inherently non-reactive,
for example, common esters, and do not feature any side
groups suitable for click modifications. In 2014 the group of
Theato transferred the synthetic approach of Yang and
Birman,15 utilizing 1,2,4-triazole (Tz) and 1,8-diazabicy-
clo[5.4.0]undece-7-ene (DBU) as organo activators, to polya-
crylates opening up a new pathway for post-polymerization
modification of non-activated ester side chains.16
Benzyl 2-diazoacetate18
Benzyl alcohol (21.73 g, 2.0 mmol, 1.0 equiv.) and 2,2,6-tri-
methyl-4H-1,3-dioxin-4-one (28.59 g, 2.0 mmol, 1.0 equiv.)
were heated at reflux in 50 mL toluene. After 20 hours, the
solvent was removed and the residue was used in the next
step without further purification. The residue containing
benzyl acetoacetate (37.20 g, 1.9 mmol, 1.0 equiv.) was dis-
solved in 100 mL acetonitrile and triethylamine (29 mL, 2.1
mmol, 1.1 equiv.) was added. Next, a solution of tosylazide
(35.77 g, 2.5 mmol, 1.3 equiv.) in 150 mL acetonitrile was
added dropwise. The resulting reaction mixture was stirred
for 16 hours, followed by addition of lithium hydroxide
(9.27 g, 3.9 mmol, 2 equiv.) in 170 mL distilled water. The
mixture was finally stirred for 4 hours, filtrated, and
extracted three times with diethylether. The combined
organic phases were washed with brine and dried with mag-
nesium sulfate, followed by solvent removal. The obtained
residue was purified by column chromatography [petrol
ether/ethyl acetate (4:1)@SiO2; Rf 5 0.8]. Yield: 15.34 g yel-
low liquid (0.87 mmol, 45%). 1H NMR (300 MHz, CDCl3, d):
7.37 (s, 5H, CHar), 5.22 (s, 2H, CH2), 4.81 (br. s, 1H, CH); 13C
NMR (75 MHz, CDCl3, d): 135.9 (Car), 128.6 (CHar),128.3
In this study, we describe the evaluation of functional
polymethlyenes in view of their accessibility to post-
polymerization modification using amines as substituents. To
the best of our knowledge, this is the first time that func-
tionalized polymethylenes have been investigated in a post-
polymerization modification approach. Scheme 2 shows the
concept of post-polymerization modification of poly(benzyl
2-ylidene-acetate) using amines as substituents. Further-
more, we will compare the resulting products to the prod-
ucts obtained from polyacrylates and highlight the observed
differences.
EXPERIMENTAL
Materials and Methods
All chemicals were commercially available and used as
received without further purification. Stated yields refer to
the purified and isolated products. [(L-prolinate)RhI(1,5-
dimethyl-1,5-cyclooctadiene)] was prepared as described in
literature.17
SCHEME 2 Post-polymerization modification of functionalized
polymethylenes, containing ester-groups, with amines as sub-
stituents. [Color figure can be viewed in the online issue, which
is available at wileyonlinelibrary.com.]
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General Procedure Using Bulk Conditions
A round bottom flask was charged with 1.0 equiv. of polymer
C1 or C2 and 25 equiv. of amine.
RESULTS AND DISCUSSION
Synthesis and Characterization of C1 and C2 Polymers
Poly(benzyl acrylate) (C2) was obtained by free radical
polymerization of benzyl acrylate with 1 mol% AIBN in diox-
ane (Scheme 3). Poly(benzyl 2-ylidene-acetate) (C1) was
synthesized in chloroform according to known procedures.20
In brief, the polymerization was conducted with benzyl 2-
diazoacetate as the monomer and 2 mol % (L-prolinate)
RhI(1,5-dimethyl-1,5-cyclo-octadiene)] was utilized as the
catalyst.
SCHEME 3 C2 polymerization of benzyl acrylate and C1 poly-
merization of benzyl 2-diazoacetate as well as their reaction
with primary amines leading to amides or imides as main
products.
Both polymers were fully characterized by 1H NMR, 13C
NMR, IR spectroscopy, and SEC (see Supporting Information)
and selected polymer data are listed in Table 1.
Both polymers showed a relatively broad molecular weight
distribution and exhibited high molecular weights. Therefore,
we anticipate similar and comparable polymer characteristics
solely differing in density of the benzyl esters, which might
affect reactivity. This functional density difference originates
by the two different types of polymerization (C1 and C2
polymerization). With suitable starting materials in hand,
we aimed in the next step for studying appropriate post-
polymerization modification conditions.
(CHar), 128.2 (CHar), 66.5 (CH2), 46.4 (CH); FTIR (ATR) m~
(cm21) 5 2106, 1683, 1386, 1351, 1171, 1003, 737, 696.
Poly(benzyl 2-ylidene-acetate) (C1)
Benzyl 2-diazoacetate (2.48 g, 14.10 mmol, 50 equiv.) and
[(L-prolinate)RhI(1,5-dimethyl-1,5-cyclooctadiene)] (0.10 g,
0.28 mmol, 1.0 equiv.) were separately dissolved in 7.5 mL
chloroform each.19 The catalyst solution was rapidly added
to the monomer solution and the resulting reaction solution
was stirred for 22 hours at room temperature. Yield: 1.22 g
1
colorless solid (8.24 mmol, 58%). H NMR (300 MHz, CDCl3,
Post-Polymerization Modification of C1 and
d): 6.92–7.25 (m, 5H, CHar), 4.73 (br. s, 2H, CH2), 3.60 (br. s,
1H, CH); 13C NMR (75 MHz, CDCl3, d): 170.9 (COO), 135.7
(Car), 128.1 (CHar), 66.8 (CH2), 45.1 (CH); FTIR (ATR) m~
(cm21) 5 1727, 1155, 981, 733, 694.
C2 Polymers
In order to modify both polymers, we first investigated the
use of 1 equiv. 1,2,4-triazole (Tz) and 3 equiv. 1,8-diazabicy-
clo[5.4.0]undec-7-ene (DBU) as organo activators for acyl
transfer reactions, following a recent publication that utilized
polyacrylates as starting materials.16 This organo catalytic
system successfully converts non-activated esters to amides
in amidation reactions.15 As the solubility of both starting
materials in dimethylsulfoxide is poor, we changed the sol-
vent to anisole as a mid-range polar solvent.
Poly(benzyl acrylate) (C2)
Polymerization was conducted by free radical polymerization
of benzyl acrylate (3.51 g, 21.6 mmol, 1.0 equiv.) with azobi-
sisobutyronitrile (0.03 g, 0.21 mmol, 0.01 equiv.) (AIBN) as
the initiator in 20 mL 1,4-dioxane at 95 8C. The polymer was
purified by repeated precipitation into methanol. Yield:
2.42 g colorless solid (14.92 mmol, 69%) 1H NMR (300
MHz, CDCl3, d): 7.25 (br. d, J 5 4.6 Hz, 5H, CHar), 4.96 (s, 2H,
CH2), 2.36 (s, 1H,CH), 1.24–2.02 (m, 2H, CH2CH); 13C NMR
(75 MHz, CDCl3, d): 174.2 (COO), 135.8 (Car), 128.5 (CHar),
128.1 (CHar), 66.4 (CH2), 41.3 (CH), 35.0 (CH2CH); FTIR
(ATR) m~(cm21) 5 1727, 1455, 1151, 735, 695.
Post-Polymerization Modification of C2 Polymer
First, we investigated the conversion of poly(benzyl acrylate)
C2 with 3 equiv. n-hexylamine in the presence of the Tz/
DBU system and observed an ester conversion of 87.5% ac-
cording to 1H NMR (bottom spectrum Fig. 1). The 1H NMR
spectrum exhibited the expected alkyl chain signals, which
were a direct result of the successful amidation reaction.
Post-Polymerization Modifications
All post-polymerization modifications were conducted for a
reaction time of 17 hours at 120 8C. Purification was done
by dialysis against methanol/dichloromethane (1:1, v/v).
TABLE 1 Summarizing Characteristic Polymer Data of C1
and C2
General Procedure Using Acyl Transfer Reagents
A round bottom flask was charged with 1.0 equiv. of polymer
C1 or C2 dissolved in anisole, 1.0 equiv. 1,2,4-triazole (Tz),
3.0 equiv. 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and 3.0
equiv. of amine.
Mn
Mw
Dispersity
Yield
(%)
Polymer
(g/mol)
(g/mol)
(Mw/Mn)
C2
C1
25,000
68,000
96,900
3.9
4.6
69
58
316,200
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TABLE 2 Investigated Amines for Post-Polymerization Modifica-
tion of Non-Activated Ester Polymer C1
Amine
Conversion in bulk reactiona (%)
Hexylamine
82b
35
75b
2-Ethylhexylamine
Piperidine
Dihexylamine
Benzyl amine
0
ndbc
a
Conversions calculated by 1H NMR do not account for the proposed
imide formation.
b
Greater than 50% according to IR spectrum (vide infra).
c
Not determined (nd) due to signal overlapping.
FIGURE 1 1H NMR spectra showing the successful amidation
of poly(benzyl acrylate) C2 with 3 equiv. n-hexylamine and Tz/
DBU mediation (C). For comparison, the 1H NMR spectra for
poly(n-hexyl acrylamide) (B) and poly(benzyl acrylate) (A) are
illustrated as well. All spectra were recorded in CDCl3. [Color
figure can be viewed in the online issue, which is available at
wileyonlinelibrary.com.]
Furthermore, a shift of the original ester C@O stretch vibra-
tion mode at 1727 cm21 to smaller wave numbers upon
amide formation (1640 cm21) was recorded. Higher reaction
temperatures resulted in increased conversions, as can be
seen in the IR spectra.
Next, we aimed for a comparison of these data with data
obtained for modification reactions of the C1 polymer poly
(benzyl 2-ylidene-acetate).
In the absence of the organo activators Tz/DBU, when solely
heating C2 dissolved in anisole with 3 equiv. n-hexylamine,
we observed no conversion at all after the same reaction
time. Hence, the clear difference in conversion highlights the
importance of Tz/DBU in case of polyacrylates of non-
activated esters. However, if we run the amidation under
bulk reaction conditions (25 equiv. amine), a conversion of
at least 74% was obtained without additional catalyst. The
corresponding infrared spectrum presents the typical vibra-
tion modes for amides, including the NH-stretching and
bending vibration modes at 3287 and 1543 cm21, respec-
tively (Fig. 2).
Post-Polymerization Modification of C1 Polymer
Experimental details regarding post-polymerization modifica-
tion with n-hexylamine, piperidine, and benzylamine will be
discussed in the following as they show the most promising
and interesting results regarding conversions, functionality,
and size. Further analytic data are summarized and dis-
cussed in the Supporting Information (i.e., TGA, DSC, SLS).
The investigated amidation reactions with various amines
are listed in Table 2. Noteworthy, determination of the
molecular weights by SEC was not successful using chloro-
form as eluent as for the starting material, but all polymers
have been dialyzed with a membrane of MWCO 5 6000 prior
characterization, hence guaranteeing that only high molecu-
lar polymers have been obtained and analyzed. Analysis by
SEC using tetrahydrofuran as eluent resulted in an Mn of
15000 g/mol and Mw of 34900 g/mol for functionalization
using n-hexylamine utilizing bulk conditions with no addi-
tional catalyst and solvent. As comparative analysis via SEC
was rather unsatisfactory due to different eluents, analysis
via SLS has been performed and is depicted in the Support-
ing Information. These analytical data were measured from a
different batch of polymer and therefore solely shown in the
Supporting Information. They show the anticipated decrease
in molecular weight upon functionalization.
Utilizing the same reaction conditions as for the functionali-
zation of poly(benzyl acrylate) C2 with n-hexylamine, involv-
ing the organo-activators Tz/DBU, on poly(benzyl 2-ylidene-
acetate) C1 results in a conversion of roughly 60%, therefore
being less effective as for polymer C2. However, in the
absence of the organo activators Tz/DBU and solely heating
the polymer with 3 equiv. n-hexylamine, led to a conversion
of at least 30%, suggesting a sterical hindrance regarding
FIGURE 2 Infrared spectra of C2 (red solid line) and C2 after
reaction with 25 equiv. n-hexylamine at 100 8C (black dashed
line) and 120 8C (blue dotted line) (C). Reactions were done in
bulk for 17 hours. [Color figure can be viewed in the online
issue, which is available at wileyonlinelibrary.com.]
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Taking these data into account, we propose the predominant
formation of cyclic imides consisting of 5-membered rings in
case of polymer C1, compared with the commonly observed
amide formation in case of polymer C2 (Scheme 3). An exact
conversion which counts for predominant imide formation
and minor amidation was not calculated as the exact ratio
between amide and predominant imide formation is impossi-
ble to calculate. However, according to the IR spectrum,
more than 50% of the converted ester moieties were trans-
formed to imides. Noteworthy, earlier studies by de Bruin
et al. showed formation of similar 5-membered ring anhy-
drides upon ester cleavage.20 While this cleavage at high
temperatures leads to insoluble polymeric materials, appa-
rently due to crosslinked materials, imide formation seems
to occur predominantly within the chain and not between
different chains. This supports the anticipated formation of
5-membered cyclic imides.
In order to proof the formation of imides, we investigated
piperidine as a secondary amine in the amidation reaction.
In case of secondary amines, no imide formation is possible
and both vibration modes of the formed amides for polymer
C1 and C2 are anticipated to be observed at the same wave
number. That this expectation is indeed correct can be
observed in Figure 4. The amides formed by substitution of
benzyl ester side groups with piperidine resulted in a C@O
stretch vibration mode at 1626 cm21 for both polymers C1
and C2. Consequently, this data can be seen as proof for a
predominant imide formation in case of post-polymerization
modification of poly(benzyl 2-ylidene-acetate) C1 with pri-
mary amines.
FIGURE 3 (A) 1H NMR spectra in CDCl3 of poly(benzyl 2-yli-
dene-acetate) C1 before (top) and after (bottom) reaction with
25 equiv. n-hexylamine. (B) Proposed imide structure. (C) Infra-
red spectra of polymer C1 before (red solid line) and after reac-
tion with 25 equiv. n-hexylamine at 100 8C (black dashed line)
and 120 8C (blue dotted line) All reactions were done in bulk
for 17 hours. [Color figure can be viewed in the online issue,
which is available at wileyonlinelibrary.com.]
the functional mechanism of Tz/DBU in case of the poly-
methylene polymer C1. At the same time, the successful
partial conversion without organo activators suggests a cer-
tain tension of the C1 polymer backbone, resulting in an
increased reactivity when compared with C2 (no conver-
sion). Next, experiments to increase the conversion of C1
were conducted and we therefore investigated the overall
conversion in absence of solvent. Bulk reaction with 25
equiv. n-hexylamine resulted in the highest conversion
(82%) of C1, calculated for anticipated amidation of the
polymer. The recorded data revealed an unexpected differ-
ence between the polymers C1 and C2. As illustrated in the
IR spectra in Figure 3, the ester carbonyl stretch vibration
mode at 1727 cm21 decreased upon conversion with n-hex-
Regarding the ratios of both C@O stretch vibration modes,
resulting from the starting benzyl ester and the formed
piperidyl amide, the reactivity of both polymers C1 and C2
can be estimated. Again, the C1 polymer showed significant
higher conversion (>50%), possibly due to tension resulting
from high functional side chain density. Besides, n-hexyl-
amine and piperidine, we considered benzylamine as a third,
very interesting substituent to gain deeper insight into the
issue of steric hindrance regarding post-polymerization
ylamine. Furthermore,
a new band was observed at
1692 cm21. Comparison of these spectral data with the spec-
tral data obtained for polymer C2, vide supra, depicts a tre-
1
mendous difference. By examination of the recorded H NMR
spectrum, the attachment of alkyl chains can be observed.
However, the IR spectrum of the obtained product revealed
the absence of NH-stretching band as well as bending vibra-
tion modes. Besides, the C@O stretch vibration mode of the
resulting product was only shifted from 1727 to 1692 cm21
,
exhibiting a shorter wave number-shift as in case of polymer
C2. Noteworthy, both starting polymers C1 and C2 were
characterized by the same wavenumber 1727 cm21 for the
C@O ester stretch vibration mode (see ESI for both complete
IR spectra of C1 and C2). Hence, the same vibration mode
would be expected for a potentially formed amide.
FIGURE 4 IR spectra of poly(benzyl 2-ylidene-acetate) C1 (red
solid line) and poly(benzyl acrylate) C2 (black dotted line) after
reaction with 25 equiv. piperidine in bulk at 120 8C over night.
[Color figure can be viewed in the online issue, which is avail-
able at wileyonlinelibrary.com.]
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ACKNOWLEDGMENTS
T. Krappitz gratefully acknowledges the support by the
German National Academic Foundation. B. Fischer, University
of Hamburg, is gratefully acknowledged for help with the light
scattering measurements.
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1
conversion cannot be calculated by H NMR in this case, due
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version higher than 50% by comparing the C@O stretch
intensities of the ester and imide moieties (Fig. 5). We attrib-
ute this post-polymerization accessibility to a certain tension
induced on C1 polymer chain.
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CONCLUSIONS
ꢀ
Tejel, M. P. del Rıo, J. N. H. Reek, B. de Bruin, Angew. Chem.
2012, 124, 5247–5251.
To the best of our knowledge, this is the first time that the
concept of post-polymerization modification using ester-
amine chemistry was transferred to functional polymethy-
lenes. Amidation of non-activated esters by primary and sec-
ondary amines has been investigated, proving the general
feasibility of post-polymerization modification in view of
steric hindrance, resulting from high functional densities of
ester groups on the polymethylene backbone. Furthermore,
the differences in amidation reactions between C1 and C2
polymers were shown and we observed a predominant for-
mation of cyclic imides consisting of 5-membered rings in
our study on polymethylene functionalization when reacted
with primary amines.
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