Effect of stoichiometric imbalances on the melt condensation polymerization of poly(dodecamethylene terephthalamide) studied by intrinsic viscosity and ¹³C‐NMR

Abstract

Poly(dodecamethylene terephthalamide) (PA‐12,T) was synthesized by melt condensation polymerization of 12,T salt with 0, 1, 3, 5, or 10% molar excess of 1,12‐diaminododecane (DA), terephthalic acid (TA), or benzoic acid (BA). Intrinsic viscosities (IV) (0.5 g/dL in 96% H2SO4 at 25°C) were measured to determine relative molecular weight differences. IV was highest for reactions containing 1 and 3 mol % excess DA (1.36 and 1.31 dL/g, respectively), followed by the product of pure 1 : 1 salt (1.25 dL/g). For all concentrations of excess TA and BA, IV was decreased. 13C‐NMR chemical shifts for DA, TA, and BA end groups were identified and their concentrations determined by comparison with the intensity of main chain polymer peaks. A log–log plot of IV versus number average molecular weight calculated from 13C‐NMR data shows a linear trend with Mark‐Houwink constants of K = 55.8 × 10−5 dL/g and α = 0.81. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

One‐pot synthesis of polyamide 12,T–polyamide‐6 block copolymers

“…At 200 °C for 1, 2, and 4 h, the intrinsic viscosity (IV) of the McI was 0.75, 0.74, and 0.77 dL/g, respectively, after soxhlet extraction and reprecipitation. This corresponds to molecular weights of 7100–7500 g/mol based on Mark–Houwink solution constants developed for PA‐12,T 14. As no variation was found within the studied times, 4‐h experiments were chosen to ensure formation of a homogenous McI solutions for anionic polymerization.…”

“…However, small amounts of excess diamine in both cases resulted in higher molecular weight. This result is attributed to the volatilization of diamine from the reaction mixture causing a stoichiometric imbalance 14. Adding small amounts of diamine to the initial reaction mixture compensates for this effect, resulting in a higher molecular weight product.…”

Study on melting and polymorphic behavior of poly(decamethylene terephthalamide)

“…The number average molecular weight was estimated with Mark–Houwink eq 2. where η sp is the specific viscosity, η rel is the relative viscosity, and C is the concentration. The Mark–Houwink constants K = 5.58 × 10 −4 dL g −1 and α = 0.81 were developed for poly(dodecamethylene terephthalamide) (PA 12T), and hereby used for PA 10T estimation because they have similar molecular structures …”

Fluidity improvement of semiaromatic polyamides: Modification with oligomers

“…Peaks were assigned according to lit. 42,43 Considering the low sensitivity of 13 C-NMR, terminal carboxylic acid group with higher concentration was chosen to be a reference to determine the concentration of phenyl groups deduced from benzoic acid. Terephthalic end groups (Tx) appeared at 133.27, 130.68, and 127.38 ppm, and benzoic end groups (Bx) appeared at 135.17, 133.83, 129.61, and 126.97 ppm.…”