I2C polling method

Hello everyone,

 I am using MSP430F5335 to communicate with battery bq40z50 through i2c communication using pollin method. I have implemented my code as follows

uint8_t data = 0x09;
void i2c_init()
{
    UCB0CTL1 |= UCSWRST;                   // Enable SW reset
    UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC; // I2C Master, synchronous mode
    UCB0CTL1 = UCSSEL_2 + UCSWRST ;            // Use SMCLK, keep SW reset
    UCB0BR0 = 10;                             // fSCL = SMCLK/10 = 100kHz
    UCB0BR1 = 0; 
    UCB0CTL1 &= ~UCSWRST;                     // Clear SW reset, resume operation
}
void i2c_write()
{
    UCB0I2CSA = 0x0b;                         // Slave Address is 0bh
    UCB0CTL1 &= ~UCTXSTP;                     //clear stop condition
    write();
}
void write()
{
   UCB0CTL1 |= UCTR;          // Enable transmit
   UCB0CTL1 |= UCTXSTT;       // i2c start
   
  while(UCB0IFG & UCNACKIFG)    //if nack rx
  {
    UCB0IFG &= ~UCNACKIFG;
    UCB0CTL1 |= UCTXSTP;       //stop condition
  }
  while(!(UCB0IFG & UCB0TXIFG)); //wait for tx begun (buffer ready)
  UCB0TXBUF = data;    
}

in this implementation i always get NACK from the slave. I also checked in the BSP code its working fine, from i concluded there is no hardware problem. in interrupt method also i tested its working fine, but my requirement is polling method only. If i put the delay in before sending byte to Tx buff its working fine. Is it correct way? Also while receiving time NACK set means whether the slave not send proper data or else problem with master.

Thanks in advance